My fiancee’s bro is a druggie. I’ve tried to talk to him but he just blows me off. Her parents can’t control him but they let him stay in the house. I have said something and they all told me to mind my own business. I think it is my business if this guy is going to be a relative.
It's really not your business unless you are going to be living with him or have him into your home, which I would not recommend. They are defensive, and even though your intentions were good, they feel embarrassed and ashamed that they are powerless. That turns to anger.