Booking Tickets for European night trains

Similarly to booking tickets for daytime express trains, there are two elements to how the price is calculated for journeys by night trains, / sleeper trains, that convey couchettes and sleeping cabins in addition to seats;
(1) the charge for making the journey AND
(2) a reservation charge for the type of accommodation you will be travelling by - though on sleeper trains the reservation is always mandatory.

Another a key difference to booking day trains, is that the reservation charges for places in couchettes and sleeping cabins / compartments are the larger element of the total price.

The accommodation types are explained in detail on the general guide to taking a night train.

• Couchettes = Compartments behind a door which house 4 to 6 beds with pillows and sheets, because travellers remain in their daytime clothes; No toilets, sinks/basins or showers within the compartment; The new type of Nightjet trains have Mini-Cabins for solo occupancy.
• Sleeping cabins = Compartments behind a door which house 2 to 3 beds, which can also be occupied by solo travellers, with full bedding of blankets / duvets; Sinks/basins included in all compartments, some also have toilets; Deluxe/Comfort cabins also have showers.

This guide is for trains which are specifically used for night trains, that convey couchettes and sleeping cabins,

Each ticket agent will apply its own booking path for purchasing journeys by night trains and there are also differences in the types of accommodation on offer on each train / route.
Hence much of the content on this guide will focus on the most commonly encountered scenarios, but they may not apply to all experiences of booking tickets.

(1) On many booking services the cheapest price, which will be the seat price, will be the first price displayed, you will only see the prices of travelling in a couchette or sleeping cabins, after you have initially clicked on this seat price.

(2) Though along the booking path and at the checkout screen, pre-payment, many ticket booking services including DB and now OBB combine the journey and reservation fees into one total price.

(3) If you will be travelling in Eastern Europe there may be no difference in price between booking online, or at the station; or the price difference can be the equivalent of only a few euros.

(4) Tickets to travel on most overnight trains, including all those in Western Europe, can now be booked online - and this has been made easier on the latest versions of the booking services.

There are there big pluses for booking in advance;

1. You can increase your chances of travelling in your first choice of accommodation.
   Some types of accommodation can sell out days (even weeks) in advance, particularly in the summer months.
   So if you want to travel in a couchette or a particular type of sleeping cabin, try to avoid booking last minute at the station.
   (Though the full choice of additional fees for single occupancy etc can be hard to track down on some online ticket sites).

2. On many routes, limited numbers of advance discounted tickets are available, as they are on day trains, so when these tickets have sold out the price rises.
   On the Nightjet trains the reservation fees also increase in line with demand, so they can also be cheaper if you book ahead.

3. Couples, pairs, small groups of travellers who want to share a couchette compartment or sleeper cabin/ compartment should book as soon as possible - particularly on all Nightjet trains, as this will increase the possibility of being placed together.

Not only can 'Private Couchette' compartments sell out, but if you can't be 'housed' together - because the only places still available are in multi-occupancy compartments, in which a place has already been assigned to at least one other person - the booking will proceed regardless.
You will have reserved, two, three, four etc places, but they may actually be in separate cabins / compartments.

What can be less clear cut is whether taking an overnight train will save you money compared to spending a night in a hotel or hostel?
A broad answer is that the ticket price (journey + reservation fee) of travelling in a couchette is usually more expensive than a shared room in a hostel, and a 1 bed sleeping cabin is more expensive than a typical 3-4* hotel room

These nine things are particularly worth knowing:

(1) Avoid gambling on booking a bed in a multi-occupancy sleeping cabin and assuming that you may have it to yourself.
This scenario is very unlikely as it is in the train operator’s interest, to ensure that those who have paid for the privilege to have a cabin to themselves, are then the only people on the train who have that luxury.

(2) There is USUALLY a big price difference (€40+) between a two bed sleeping cabin and a single bed/occupancy cabin.
Unsurprisingly most solo travellers don’t relish the prospect of sharing a ‘bedroom’ for the night with a stranger.

However, book a single cabin and you will be primarily paying a premium for your privacy.
The bed and cabin won’t usually be any larger or any more luxurious.
More often than not, 1 person cabins are no different to other sleeping cabins, the other beds in the cabin will usually be stowed away or left vacant.

However, the Caledonian Sleeper trains are an exception to this, none of its sleeping cabins have more than two beds, but its Club Rooms (cabins) are more luxurious than its Classic Rooms, partially because the Club Rooms have an en-suite shower.

Also on the Nightjet new generation trains, Mini Pods are available with private individual beds,

(3) As you’d expect when sleeping cabins with a shower are an option, they’re more expensive than standard sleeping cabins, but you will be primarily be paying this premium price in order to have a shower.
The Deluxe/1st class/’Premium cabins aren’t usually otherwise more luxurious than the standard sleeping cabins.
Though the Nightjet new generation trains have Comfort Plus cabins which have showers and these are larger than the other sleeping cabins on this type of train.

(4) Even when booking more than two months ahead, some of the sleeping cabin options typically offered on a route may not be available.
This can seem random, particularly in terms of the availability of one or two bed cabins.

This is because on most routes and services, there aren't special sleeping cabins on the train, which are permanently set up for solo or double occupancy.
The majority of sleeping cabins are equipped with three bunk style beds, one or two of which can be folded out of use, so that they can offered as 1 bed or 2 bed cabins
So when the demand is high for places on the train, the operator can accommodate more people and increase its revenue by only offering 3 bed cabins
Hence fewer places are ever made available for one and two person occupancy.

Also take note if you will be travelling solo with an Interrail or Eurail pass - Before you booked your pass, you will have seen a reservation fee price for a 1 person sleeping cabin, but you can't assume that it then be available to book on the train you want to take.

(5) Though if you will be travelling solo and want a one-bed cabin, or will be travelling as a pair and want a two-bed cabin, don't assume that Deluxe cabins with showers will be available for booking - unless you will be taking a Nightjet New Generation train.

Having looked up numerous journeys, the Deluxe cabins with showers were more often than not, only available for 3 person occupancy.
On all of these departures a one or two bed cabin with a shower could have been offered, as they're the same cabins with the unoccupied beds folded out of use - but they weren't.

(6) If you generally fall asleep when travelling long distance on a daytime train, there are coaches with ‘day’ seats available on all sleeper trains - there are typically more places available than in the sleeping accommodation.
You may have as much sleep as you would in a couchette and you will typically save around €25, by only paying a reservation fee for the seat, rather than a couchette

(7) When booking tickets at a station booking office be clear whether you want to travel in sleeping cabin, couchette or ordinary seat.
If you don't specify the type of ticket you require, the default tickets that you may be sold may only be valid for travel in ordinary seats.

(8) On many routes, the overnight trains are much slower than daytime trains, they make longer, less direct journeys and they can’t travel on the high speed lines etc.

(9) If you want to travel as a group take care when booking online - hence the separate guides, which you'll find below.

ÖBB is the national rail service in Austria and it operates the Nightjet services on routes from and to both Austria and Switzerland, but its booking service also sells tickets for the EuroNight services from and to Austria.
So the night trains on these core routes can be booked on the OBB website:

• Wien/Vienna ↔ Amsterdam, Berlin, Bruxelles, Buccuresti, Firenze, Hamburg, Hannover, Koln/Cologne, Krakow, Kyiv, Lviv, Milano (until Dec 13th 2025), Przemysl, Roma, Utrecht, Venezia, Warsaw and Zurich
• Munchen/Munich ↔ Amsterdam, Budapest, Firenze, Krakow, Ljubljana, Milano (until Dec 13th 2025) , Przemysl, Roma, Utrecht, Venezia, Warsaw, Wien/Vienna and Zagreb
• Innsbruck ↔ Amsterdam* Firenze*, Hamburg, Milano Roma, Utrecht and Zurich
• Zurich and Basel ↔ Amsterdam, Budapest, Graz, Hamburg, Utrecht and Wien/Vienna

The journey look-up process on the OBB booking service doesn't give the opportunity to specify that you want to travel by a night train.

So if you want to take the night train you'll need to select it from the choice of journey options.
Hence it can be worth being aware of...

1. The night trains can use different stations to the day trains, so a general city has been deliberately selected as a destination, as this can increase the possibility of seeing a direct night train among the journey options.
2. The OBB booking service doesn't use specific symbols to indicate night trains, though two types of night train service travel from and to Austria, Euronight trains and Nightjet trains - So to find the night train amidst the journey options. look out for EN followed by a train number, or as in this example, NJ followed by a train number.
3. A gap in this line across the data indicates an indirect journey option; An overnight end-to-end journey can often be quicker if an early morning connection is made into a high-speed train on to the destination.
4. No gap in this line indicates a direct journey.
5. To proceed on to the booking, click on the red box; The price shown here will be the price of travelling in a seat.
6. These warning messages on the grey background won't always be present.

On this latest version of its booking service, OBB is evidently going the extra mile to explain the different types of accommodation on the night train.
When clicking on the red price buttons, this breakdown of the accommodation types may appear - it can be inconsistent.
The idea is that you

1. Read though the options, decide whether you want to travel in a seat, couchette or sleeper,
2. Then click on which of the three options meets your needs.
   Though this doesn't particularly matter, as will be seen below, at the next step, swapping between the seat, couchette and sleeper options, is easily done.

Regardless of the type of accommodation selected on that pop-up of the different options, this will be the next page that you will be taken to.
In effect this page has two functions

• One is another means of choosing the accommodation option; on the notes above, 1 = seats, 2 = couchettes / Mini Pods, 3 = sleeper cabins.
• The other is the type of ticket, as no matter matter whether seats, couchettes or sleeper is selected, there will be three types of ticket to choose from - Non Flex, Semi Flex and Flex.
  Hence what the arrows are indicating, is that having clicked the type of accommodation, you will look down the page to see the same three types of ticket, regardless of whether you want to travel in a seat, couchette or sleeping cabin.

The 4 is being used on the example to emphasise that whether your booking can be refunded etc, is based upon the type of ticket you select and not the type of accommodation you have chosen.
The 5 indicates that you can have a repeat viewing of the accommodation summary box, if you click this 'train infrastructure and details' link.

Taking a night train can be expensive, so it's particularly worth taking a close look at the terms and conditions of your booking - especially if you'd be happy to pay a higher price to have more flexibility over the booking.
Hence, before you click..

1. ...'Pick this service' in order to go on to the next booking step, it's a good idea to...
2. ...click on 'Service Details' as this will give you more info about the ticket - and not the train.

If you want to travel in a seat on the night train, two things to be aware of, are:

1. You will be assigned a specific seat(s), though you won't be able to select specific seats on a sleeping plan.
2. Once you have chosen one of the two options, you can access further info and move on to the next stage of the booking process.

If you want to book a place in a couchette, this is how the info and options will be presented on the OBB website.
What has been pointed out above is:

1. There are up to three different options for travel in a couchette - as indicated by the pale blue boxes and you will need to make a choice between them.
2. For a bunk in a 'Comfort' compartment this is the total price per person - OBB used to break down the price into segments.
3. The Comfort compartment is either (1) mixed sex - places will be shared by men, women and children, or (2) ladies only. So female travellers who will want to avoid the possibility of sharing a compartment with male travellers, will need to proactively select 'Ladies Only' - OBB won't assume that it would be your preference.
4. These 'Services Included' links are an opportunity to discover more about what's offered in each type of accommodation - see below, for examples of what you can see.
5. No matter which of the couchette options you want to travel by, you will need to click one of these 'Pick this service' buttons in order to move on to the next stage of the booking process.
6. Mini-Cabins are only available on the latest type of Nightjet train; And these trains happen to be deployed on the Wien to Roma route, which has been used for the example. Hence they have been included by OBB as a couchette option, instead of being split off into a separate category of accommodation.
7. Or the other option is to book an entire 4 berth compartment and then who travels in it is up to you; An individual can pay the cost and the avoid having to share a compartment with anybody else - Or a family group or a group of 3, or 4 friends can book it and ensure they won't be sharing the compartment with anybody else.
8. Whether a booking can be cancelled isn't anything to do with the type of accommodation selected, so check the terms of each type of ticket - Because if you will want more flexibility of how to manage your booking, it's the type of ticket which matters.
9. These higher prices are because of that increase in flexibility over the booking - And not because the accommodation will be different according to the type of ticket you select.

Key things to be aware of when booking on the OBB website, if you want to travel in a sleeper cabin / compartment are:

• The maximum number of places / beds in the cabin will be 2 or 3 depending on the type of train / sleeping car that are being used on each departure / route.
• When one person is travelling alone, the prices you will see on the OBB website are per person.
• When two people are travelling together and only 2 bed cabins are available, the price is per cabin
• But if two people are travelling together and only 3 bed cabins are available, you will see two price options, per person and the entire cabin
• In the example below, a solo traveller is making the booking, hence the option to pay more to have private / sole use of a double cabin / compartment - Note that sole occupancy of a Double Deluxe cabin is an option for solo travellers on this route.
• Note that before you choose a type of accommodation, OBB won't ask you to have entered a name or sex of the traveller on the booking path - So it won't automatically assign 'appropriate' types of accommodation options, instead you need to make the choice.
• In a major change the sleeper cabin booking options are either mixed sex, or Ladies Only - The default on OBB evidently isn't now a division of cabins by male and female, with couples who wanted to share having to click a check box.
  The default has been flipped so that a mixed sex couple can simply choose a compartment / cabin.

However solo female travellers who won't want to share a compartment / cabin with a male traveller, or pay more for sole use, now have to proactively select 'Ladies Only'
Also male solo travellers, who don't want to pay more for sole use, may discover on boarding that they are sharing the compartment / cabin with a female fellow traveller.

If a male and female travelling together want to travel in sleeper compartment, but don't want to share it, two separate bookings will be be necessary.

So if you will be travelling solo and all of the accommodation types are still available, the options are:

• travel in a seat
• the privacy of a Mini-Cabin, on the trains which have them
• sharing a couchette compartment with fellow travellers, with a Ladies Only option available
• booking a private couchette compartment, so that you have sole use of it
• sharing a sleeper compartment with fellow travellers, with a Ladies Only option available
• booking a sleeper compartment for 1 traveller.

This journey is by a New Generation Nightjet train

What has been pointed out above is:

1. A mixed gender compartment / cabin which can be shared by female / male travellers is the default - female travellers who don't want this, need to proactively select Ladies Only instead.
2. It's particularly worth clicking the 'Services included' link so that you can see what you are paying for
3. If you see 'single seat' ignore it, as it anything to do with single occupancy or where you will be sleeping (what it's pointing out is that when you use the table, one person can sit on a seat. but the other person will be sat on the bed).
4. No matter which of the sleeper options you want to travel by, you will need to click one of these 'Pick this service' buttons in order to move on to the next stage of the booking process.
5. There's usually more than one sleeping compartment option / type to choose from, so it can be worth checking them out too, you can't change your mind and switch to another option after you have booked.

This journey is by the older type of Nightjet train and it has additional sleeping compartment options compared to the newer type of Nightjet - which are:

1. a 3 passenger compartment
2. a 2 passenger compartment with a shower
3. a 1 passenger compartment with a shower

To move on to the next stage of the booking...

1. ...Once you have clicked a 'Pick this service' button - regardless of whether you want to travel in a seat, couchette or sleeper, then...
2. ... over to the right (on a PC, desktop or laptop_ you'll need to then click the red 'Continue to reservation' button

If you want to share your sleeping accommodation with a partner / friend / family member on a European night train, there are a couple of things worth being aware of when making a booking.
Plus the steps you take can vary across ticket agents, hence the specific examples further below.

Though the key things to be aware of are:

• Most sleeping cabins on European night trains are fitted with 3 beds, but they're also offered for booking for occupancy by 2 people.
• Though on many of these trains, including virtually all EuroNight services, these are the same cabin - Two people in a cabin means greater privacy etc, so the cost per person will be higher
• However, at busy travel periods, they can seemingly only be offered as three bed / place cabins, so it may not be possible to reserve a place(s) in a 2 bed cabin when you book: Or the places in 2 bed cabins / compartments can be sold out with the places in a 3 bed cabin stil being available
• On some trains, including the newer type of Nightjet train, sleeping cabins / compartments aren't offered with 3 beds/ places, so this isn't something that those who want to occupy as a pair, need to be concerned with when making journeys by these trains.

On some train services which only have a maximum of two beds / places in a sleeping cabin, including Caledonian Sleeper and Treno Notte trains, when you book you are in effect purchasing the cabin / compartment.
Hence in this scenario one booking for two people means that you will be sharing and you can split the cost between you, post-payment if that suits you.

However, on other trains, including the Nightjets, you will instead be booking two places in the train's sleeping cabins.
You may asked if the two travelers on the booking want to share, which is a likely scenario on Euronight trains, but you won't be asked if you want to share when booking a journey on a a Nightjet.

How the sleeping cabins on the Nightjet trains are segregated has recently changed, it used to be male or female - meaning that couples who wanted to 'break this rule' would be asked when booking, if they wanted to share.
However, now the accommodation is split into mixed sex and Ladies Only compartments, with a probable factor being that it now makes it easier for the sleeping cabin/compartment to be assigned to a couple / pair.

Although having selected a 2 bed compartment for two adults when making a booking for two people, you might assume that you will be assigned both of the places in one cabin, so that the two people on the booking can can share it.
Most of the time you would be correct to assume this, particularly if you book ahead, but it isn't absolutely guaranteed.

Solo travellers also need to be accommodated on the train, but they may have not been given the option to book a single occupancy cabin, or wanted to pay a premium for a 1 person cabin.
So in a scenario when second beds are available in cabins in which one bed has been booked by another traveller - and these are the only bookable option at the time when a pair book together, then the beds you will be assigned may be in separate cabins.
However, if this is the situation, you won't be made aware of it when you book.

Which is why, as shown above, the DB website flags the possibility of not being accommodated together, when two people are making a booking for sleeping cabin accommodation on a Nightjet.

For this reason two women travelling together who want to share, should still take care to select 'Ladies Only' when booking on the OBB website.

On the Nightjet booking service, before selecting the accommodation options, there will be a link to what is offered when booking 'Private' sleeping compartments - note that it is an info link, it isn't a booking link.
The core info that can be accessed is how to not having to share a sleeping compartment / cabin when two (or more) people are included on the one booking.

However, as shown above,

1. Seemingly on the booking page for any journey by a Nightjet train, and more than dozen journeys were looked up, this 'warning' that other travellers may be in the cabin / compartment will be shown - Even if two people booking together choose a 2 person sleeping cabin/ compartment.
2. Despite the warning, the option to book a 'Private cabin' isn't ever seemingly made available.

On the similar page for booking the couchette accommodation, a similar 'warning' is shown, despite the 'Private compartment' being a separate booking selection, but on the sleeping cabin booking page, it seemingly isn't there.

OBB operates the Nightjets, so all routes by these trains can be booked on its website, regardless of whether the journey will be from or to Austria.

Having added a passenger on the booking steps so that a journey is being found for two adults, be, you won't have been given an opportunity to inform OBB that a male and female will be travelling together.
Therefore OBB will present you with all of the available accommodation options, from which you can make a choice.
Aside from 1 person cabins not being presented, these will be no different to the options that will offered to solo travellers that have been shown further up this guide.

Seemingly the logic is that you don't need to 'tell' OBB that two people want to share a cabin, because if you don't also select 'Ladies Only', it doesn't now matter that a male / female pair want to share.
However, OBB, may not be offering a share tick box / selection, because it can't absolutely guarantee that you will be sharing, though the sooner, you book the more likely it is that this will be the case.

When booking on the DB website, if you select 'Economy Comfort' or 'Standard' tickets you will be able to select the type of cabin which suits you.
Though note that DB also makes it clear that you will be selecting 'spaces' and not cabins compartments.
At the next stage of the process you will be asked to enter the names and 'sex' of the travellers, but if you let DB know that a male / female will be travelling together, you can't assume that you will be placed in a cabin together, even though you have 'told' DB that you are couple.

SBB takes a different approach to DB and OBB because it asks ticket bookers whether they are male or female prior to offering the ticket booking options.

What has been pointed out on the above screen is:

1. When booking a sleeping cabin, it makes no difference to the options you are offered if you choose first or second class.
2. Use this to assign male or female to the first traveller; the person who will be making the booking.
3. Add the second passenger here; and repeat the gender assignment

Then because you have already assigned the gender of each passenger, you will then only be offered the most logical accomodation options, which correspond to who will be travelling.

What has been pointed out on the above screen is:

1. You can check that the booking options are for two travellers.
2. You will be given the opportunity to book a berth in a couchette which you will share with two or four other travellers.
3. The sleeping cabin options will include 'two passengers in a double compartment', so if you choose this you will be sharing the compartment (So when a male and a female are travelling together and you don't want to share, you will have to book two single compartments).

When CD is one of the ticketing agents selling night train tickets for a route, using it is a good option if you want to share a two bed sleeping cabin as a couple.

As can be seen above, the accommodation selection step of its booking path, includes the following;

• an easily understood selection of a sleeping cabin (sleeper)
• the number of people in the cabin; double = 2 beds
• the opportunity to inform CD that a female and a male will be travelling together.
• and most crucially you are given the opportunity to explicitly inform CD that you want to share the cabin (when a male and female don't want to share, they can avoid ticking this box; and will then be assigned places in male only and female only cabins).

On most international EuroNight routes / services and the older Nightjet trains, when all of the accommodation options are still available, there will be a choice of travelling in:

• seats
• a berth in a couchette compartments with four bunks
• a berth in a couchette compartments with six bunks
• a place in a sleeping cabin to be shared by up to three people
• a place in a sleeping cabin to be shared by up to two people
• solo occupancy of a sleeping cabin
  with some trains also offering places in Plus/Deluxe versions of sleeping cabins, which also house showers

On the newer type of Nightjet train, there will be a choice of travelling in:

• a berth in a couchette compartments with four bunks
• booking an entire couchette compartment for 'private' use by 3 or 4 people
• a Mini-Cabin, which in effect is a small couchette for private use by one person
• a place in a sleeping cabin to be shared by up to two people
• a place in a Plus sleeping cabin with a shower, to be shared by two people.

However, as a group you'll need to decide which of these accommodation types will suit you, because when you book you will tell the website how many people will be travelling together, but you can only then choose the one type of accommodation per booking.
In effect you will be saying to the ticket agent, we will be travelling together on this train and we all want to travel in seats, or couchettes or sleeping cabins.

So, for example, if a party of six people will be making the journey, and;

• two members of the party will be happy to pay a cheaper price to travel in the seats,
• two people will be happy to share a couchette with other people outside of the group,
• one person wants to travel in a Mini-Cabin
• one person wants to travel in a sleeping cabin

You will need to make four separate bookings, taking care to ensure that you are all selecting the same train.

Booking berths in a couchette is typically simpler than booking sleeping cabins when a small group want to travel together.
A group of four travellers can choose a couchette with 4 berths, or a group of six travellers can choose a couchette with 6 berths (when available) and you often won't have to share it with anybody else.
Male and females can travel together in couchettes, so that isn't an issue if a mixed sex group wants to share.

Travelling in a couchette in in a group of five is a tad trickier, because when a 6 berth compartment is available, that remaining sixth berth may be offered to another solo traveller - if booking a private compartment isn't an option.
Plus more obviously, when only a 4 berth compartment is available, the fifth (and sixth) person in the party, will have to sleep in a separate compartment.

A party of three will almost certainly be sharing the compartment with another passenger (s).

Though what can't be guaranteed is that, despite the multiple people all being included on the one booking. you will actually be sharing the couchette together, even if the number of people matches the number of places in the couchette compartment.

Particularly on popular trains, it seems that places are assigned front to back along the length of the coach/car; Compartments are not left vacant on the system, in case a party of four or six ultimately wants to make a booking.

Which is why on Nightjet trains, you will now need to pay a higher cost specifically book a 'private compartment,' when available, in order ensure that you won't be sharing 'your' couchette compartment with anybody else.

On any European night train a sleeping cabin has a maximum number of three beds.

When booking for Nightjet journey, you can choose between places in;

• two or three bed compartments (no 3 bed compartments on the new Nightjets)
• two or three bed compartments with showers (on the new Nightjets the Comfort cabins with showers have two beds)
• Ladies Only versions of the types of shared compartments
• all members of the party can opt to spend the journey in 1 person compartments.

If all members of the party opt for the same type of accommodation, all of the travellers can be included on one booking.

Therefore logic suggests that

• when a small group will be travelling together on the same train,
• plus they all want to travel in the same type of sleeping cabin,
  that it should be possible for the travellers to assign the cabins into whatever configuration suits the group when booking.

However, this isn't possible, as the only steps are

• tell the booking service how many will be traveling
• choose one accommodation type
• and then most typically, but not always, you enter the sex, age and names of the travellers.

What doesn't happen pre-payment is being told you will be travelling in x, y or z cabins.
So you don't get an opportunity to say, 'this person + this person want to be together in cabin x' etc,

Logic also suggests that if, for example, a party of six wants to travel in two bed compartments / cabins, that three cabins will be assigned to the group (3 x 2 = 6) and then on boarding, you can decide who will share each compartment.
However, this scenario can't be guaranteed, and if it isn't the case,, you may not be aware of the situation until you board.

This is, for example, because there will be a possibility that at the time of your booking there were 4 x two bed compartments / cabins on the train, in which places were available.
However;

• Two of them may be wholly unassigned so have two places available each = for four of the travellers in the group.
• One of them may have one place already reserved by a male solo traveller.
• The fourth may have once place assigned to a a female, who has selected a place in a 'Ladies Only' compartment.

So if your party of six has a female traveller, they will be assigned the second place in the Ladies Only compartment; One of the men will be assigned the other place in the cabin already booked by the solo male traveller - with the remaining two compartments, left to be split between the other four members of the group.

When travelling with children on international European night trains, what's seemingly now the most common scenario is that the booking terms and process mirrors how tickets are sold to adults.

It used to be the case that bookings for kids could be tailored, so that for example, an Adult could decide that a 6 yr old and 8 yr old could share a bed, meaning that a ticket had to be purchased for the 6 yr old, but not a reservation.
However, what's more common now is that each booking per child aged 5 and over, has a ticket and reservation element combined - With that ticket element being €0 on the Nightjet, when an Adult books discounted Sparschiene / No Flex tickets.

These tickets and reservation costs are also most typically combined into one total price, so now this price for the entire travel party usually has to be accepted at face value.
It isn't typically possible to see a breakdown of the cost per adult and the cost per child.

The ticketing

For the ticketing element of the trip children aged x and under travel for free and children aged x and under travel at a typically 50% discount - with the terms being applied as per the operator of the train; Nightjet = Austria, CD Night = Czechia

The child rates for tickets is usually discounted by around 50% of the Adult ticket price, but children travel for free on European trains at these ages:

• under 15/aged 14 and under - in Austria and Germany; when an Adult books discounted Sparschiene / No Flex tickets
• under 6/aged 5 and under - in Czechia, Slovakia, Slovenia and Switzerland
• under 6/aged 5 and under - in Austria; when not travelling with discounted Sparschiene / No Flex tickets
• under 5/aged 4 and under - in Great Britain
• under 4/aged 3 and under - in Hungary and Poland

The reservations

Similarly to how on day trains children aged 3 to 5 won't be charged for a reservation, because of an assumption that they can share an adult's seat, they won't typically be charged a reservation fee for any of the accommodation options on a night train.

Though by not paying a reservation fee for a place in a couchette or sleeping cabin you ae in effect committing to the child sharing your bed / bunk.
If you won't want to do this when the journey is by a Nightjet / NJ trains, then it's best to book on the Nightjet website - as it gives a traveller option of 'Infants with own seat', though it also applies to Infants with own bed.

Keep in mind that the beds in sleeping cabins / couchettes are smaller than a typical single bed in a hotel.

For older children:

• aged 5 to 15 in Switzerland
• aged 5 to 14 in Austria, Czechia, Germany, Hungary and Slovakia

a difference to booking tickets for the day trains, is that the reservation fees for the night trains are discounted compared to the fees charged for Adults.
On all Nightjet services the reservation fee is 50% off whatever is being charged to Adults at the time of booking - There are no fixed fees for reservations on the Nightjet trains.

The older Nightjet trains have private compartment couchettes compartments with 6 berths, which are sold at flat rate price - the example is taken from the Nightjet ticket booking service

When travelling with two or more children they can be a good option, as booking them thereby ensures that you won't be sharing the compartment / cabin with anybody else.

Though because the price is typically based on providing a group of 3 or more adults with a good deal, it will be usually be more expensive than booking three or more places in a couchette.
However, keep in mind that even if a party of 2 adults + 2 kids books 'places' in a 4 berth couchette, or if a a party of 2 adults + 4 kids books places in a 6 berth couchette, there's no guarantee that the reservations won't be split across multiple compartments.

The newer Nightjet trains have different couchette options which can be be booked by Adult + child groups.

As can be seen on the example taken from the Nightjet booking service, for a party of 1 Adult + 2 children

1. =The cheapest option for couchette style accommodation (no washing facility in the compartment) is to book three separate Mini Cabins, one for each member of the party.
   So this can be a good option if the kids can be trusted to manage both the controls within the cabin, lighting etc, and the access cards, so that they can enter and exit by themselves.

2. = This is the option for places in a 4 berth compartment, as the new Nightjet trains don't have 6 berth compartments.
   However, despite the group including kids, the fourth place in the compartment is likely to be allocated to another passenger

3.= This is the option to ensure that you won't be sharing the larger type of couchette compartment with anybody else, despite booking a party of three into the compartment that has 4 berths

Those 'private couchettes' can be a better option than sleeping cabins, particularly if two children aged 15 and under will be travelling with an adult - because they are typically the only option for securing privacy.

As seen above - on the older type of Nightjet trains it will be possible to book a 3 person sleeping cabin, which can seem like the best option - particularly if you're willing to pay extra for more bedding, a more substantial breakfast and washing facilities in the cabin etc

However, what's been pointed out above, is:

1. As made clear on the 'warning' - which can be easily missed in the rush to make a booking, you can't be absolutely sure that you will be sharing the same compartment / sleeping cabin, despite including children in the booking.
2. That's because what's missing, as indicated by the circled empty space, is that you won't be given an option to book a 'private sleeping compartment' - which is seemingly a likely scenario, because when when running test bookings on more than 10 journeys, it was never offered.

This is an example of a booking when the journey is by the new type of Nightjet train, hence what has been pointed is:

1. The booking has been made for a party of two children aged 15 and under travelling with an adult.
2. However, on the newer type of Nightjet train the seeping compartments have a maximum of two beds / places
   Both of the children will each be assigned their own individual beds, no matter their ages, hence three beds have been booked; So, as per the 'warning message', the reservations will be split across more than one cabin / compartment
3. Despite this, as the 'warning message' points out, the other place in the second cabin may be occupied by another traveller.

Therefore on boarding you will have to decide to allocate the cabins / compartments as to what suits you;

• the two kids together, with the adult potentially sharing a cabin with somebody else
• the adult and younger child together, with the older child potentially a sharing cabin with somebody else
• all squeezing into the one cabin and making the most of it.

Which is why despite the sleeping cabin / compartment coming with benefits such as, more bedding, a more substantial breakfast and washing facilities in the cabin etc, it can make a lot of sense to compromise and book a private couchette compartment instead.