If things are in his name but still come to your address... they are still his bills. If you think you should talk with a lawyer...talking sooner before things grow, would be better then talking later.
You are right though.... they can't take what you don't have.
I have told that to a bill collector or three. They get nasty, I feed them truth. "you will get it when I get it" Sure if you can find any money in this checking account, we will share it 50/50 *LOL* They get the message (some times)