J.M.
Hi C.,
Not every car seat fits every car. I wish there was an easier way to try them out. We went through many until our current seats which fit really well. Until then I thought car seats weren't really meant to fit any cars.
As far as sitting next to two car seats:
I actually refuse to sit in the back with two car seats. Here's why: what would happen to me if someone crashed into the side of my car? The kids' car seats are so strong to protect them, I pictured myself squished and killed by their car seats. I realize this is an unlikely scenario. However, if their seats are meant to protect them in a crash, what is there to protect me?
In our three row van on a long trip, I will sometimes sit in one of the rows with one child. Of course then they argue over who gets to sit with mom...
Good luck!