Not your circus, not your monkey.
It's very hard to step away, but it sounds like that is just what you need. You are giving them a lot of power over your emotional well being that they don't deserve. Be matter of fact w/them, and steele yourself emotionally and don't participate in the aftermath. If you don't respond at all, it's very difficult for a person to continue on and on. Eventually it will stop. Gray Rock is a very useful technique.
Sending you big hugs. Work on being close to those who do treat you right, those people are family, blood or not.