xian to shangai soft sleeper

Actually, the tickets are assigned and issued randomly, and you can not choose berths as what you want. Thus, no one can 100% guarantee you stay together in the same compartment. However, if you book with a travel agency, they will try best to ensure you sleep in the nearby berths. And when they booking the berths for you, if you are assigned far away or in a different carriage, they could repeat the booking to make sure you all can be together in the same compartment. But if there are no plenty of tickets left, this might not be met sometimes.