I agree STG, I love my MIL and I can't call her mom. She's not my mom, and we're okay with that. I call her and my FIL by their first names. I hope some counseling can help you sort it out. Maybe it could become a family session, she probably needs to see some of the stress it is putting on your relationship with DF. It is very tragic that she lost her son, I wouldn't want that to happen to anyone. But, she has to understand that the other son is a grown man and is seeking to have a family of his own, and needs to act in the interest of his new family, and not necessarily his mother's.