Clover - I am sorry you are in this situation.
All I can share is my experience. I engaged my STBXAH's family about his problem (which they all knew and have issues themselves) because a part of me thought they could help and they didn't and they couldn't and he is back living closer to them and they all probably drink together in their dysfunctional alcoholic family.
I guess the question is why do you want to tell them? Are you looking for their help to help him? Are you looking for them to give you support?
Perhaps once you get to the root of what outcome you're seeking, it will help you decide what to do next.