Hey it is our first going to Spain or France and we are flying into Barcelona but meeting up with family in Toulouse. We have looked up renting a car but I heard there is a fee to drive it through different countries. I also saw there is a train but I thought I saw that you have a connection. So my question is what is the best/easiest way to make it from Barcelona to Toulouse (with a 7 year old and a 1 year old)?
It's 4:14 by train with one change, that would be the best option in my opinion. The fee for driving through different countries you mention is probably the one way rental fee that can be pretty large if you return a rental car in another country.
The rental car fee for drop off in Toulouse will be way too high, hundreds of dollars. The train will be fine, and the connection isn't tight so it is easy to make it even with kids and luggage.
Pick the train with the longest connection time.
There is bus that goes direct
https://www.flixbus.com/bus/barcelona
Your options:
https://www.rome2rio.com/map/Barcelona/Toulouse
I agree, the train would probably be the best option, as long as the connection in Narbonne is not too tight.