Whilst there are some new cross continent routes coming online, overnight rail routes have been in decline since the 1990s.
It takes quite a bit of persistence to make this work especially if travelling with a young family. For example travelling from London to Rome (although surprisingly can be done in a day) takes 16 hrs and involves 3 changes including slogging across Paris.
https://www.seat61.com is a good resource for planning trips involving European train travel.