Unfortunately there are no night trains on those routes. 

Happy new year!

There is no night train from Barcelona to Amsterdam (not even Barcelona to Paris). It's a possible daytime connection with one change at Paris (about 11 hours; little bit more). It's possible to go by night train part of the journey in France but it does mean a longer / slower journey with more changes (e.g. Barcelona to Latour de Carol, night train to Paris, connecting train to Amsterdam; about 21 hours travel time).

You may get prices and book your ticket for this here: https://www.sncf-connect.com/en-en/train-ticket (still too early for summer but you may enter your trip and you'll get a mail when it's available).

Amsterdam to Paris is just 3h 20min (best case) so a night train wouldn't make any sense. 

Get prices here: https://www.eurostar.com/rw-en (ready to book up to July 20th).

If these are not your only trips, a railpass may make sense.

Hi Hektor. Thanks for this.

I thought it’ll be good to experience this no matter the cost / time but it’s not to be. Now time to look for flights and other ways to experience europe trains

The sleeper could be a fun, and often cheap, way to travel to Paris. A group of 6 can travel quite cheaply, taking a whole sleeping compartment.

Anyway, you can read about the journey here - either 6h45 by direct TGV, or the slower sleeper option.

https://www.seat61.com/trains-and-routes/paris-to-barcelona-by-train.htm

For sure a flight Barcelona-Amsterdam will be easier. Maybe fly in one direction and train in the other?