Family of 5 in a 4-passenger cabin? Overnight train Paris to Venice.

As long as you buy that extra ticket for a seat in 2nd class, I don't think anyone would care that you kept a "visitor" in your room. Now, if you DIDN'T buy that extra ticket, that would be a different story. On the off chance that there might be some obscure rule against putting 5 in a 4-person cabin, I would just put one of the adults out in the 5th seat until all tickets were checked by the conductor, then wait until bed time and have that person join the family. No one is going to bother you after lights out. Sorry, I can't help with the luggage question...

Thank you so much that helps a lot. I going to that.

There is a luggage holding spot at Venice station. The cruise ship ports are not too far to walk with luggage from the Venice station. We did it last summer with a 7yo. In fact they have an express tram-thing from Piazzale Roma to the Cruise terminal. Santa Lucia station to Piazzale Roma is about a city block, just over a bridge with some stairs. See if you can check your luggage onto the ship holding area, then go see Venice for a few hours.

I would be concerned about space. Those bunks are narrow. A better option, if it is available, would be to buy six tickets in a 2nd-class compartment. Should cost the same, I think, as you are buying a whole compartment in either case.

Thank you. I did go ahead and bought the 5 tix for a 4 passenger car. I explained in the comments when purchasing. I was going to do the 6-car but it was 2nd class and everyone kept saying don't do second class on other reviews I read and plus we didn't want a stranger with us in the room with kids in another country because people were saying they walk around in underwear or steal. Etc. So I hoping it will be ok. Worst comes to worse, my husband will go sleep in a car with 3 other people in case they decide to kick one us out. Thanks for advice on district to cruise. I was worried at first feel better now.