That makes some sense then.
I sure hope that you can figure things out soon! You're definitely going to need a bigger space if they can't share (even with a same sex) or with their cousins.
2 floors is a LONG way to split them up, even if you installed a door. I hope you can figure something out! It's a tough go taking in someone else's kids, even family.....Like I said - I've been there!
Best wishes to you!