I think sleeping on it is very sensible.

Have you thought about getting your DH to talk to his brother? In my relationship, DH deals with his family and I deal with mine. While he's part of my family of course, I set the tone and take the lead on any 'issues' and same for him with his family. This scenario would definitely come into this category.

Your DH could possibly explore this a bit with his brother. As long as you trust him not to sell you up the river, this could be a way to resolve this.

Completely crap scenario. Hope you are doing ok.