The whole mother-in -law thing can be dealt with after things are patched up with his wife. God told man to leave Mother and Father and cleave to wife, In this case Mother in law is making that nigh impossible. She has proven that she does not want to see the relationship repaired. If she were not a problem I would not say to exclude her.We are told to withdraw from a brother who walks disorderly....this would apply. This dear couple needs help and the Mother in law is not a help.