What would you do?

My MIL and FIL finally talked to me this morning after roughly a week and told me they were moving out. We opened our house up to them in April and did everything for them. They moved here from Mississippi with the little money they had from selling their house. We supported them, paid their truck payments, paid their insurance and now they do this to us. Yet again the are choosing SO's brother over him. I can tell he is heart broken and pissed off because if they didn't talk to me today, they would have said something the day they left. Am I overreacting? My SO was about to cry and kept blaming himself for everything that has happened to us the last 3 years. What should I do. Any advice is welcome