The reality is - that as much as we speak and hope they will hear, until they WANT to listen... they never will - and the even SADDER reality is that this very seldom comes to turn.
Being family makes it a little more challenging, but even in those instances - my advice would be to ensure that you protect yourself and your own family first. Don't let them too be exposed to even a GLIMPSE of such - and by that, I mean... walking away (as hard as it can be) is often the best decision... but only you know what is best in that respect.
It is an exhausting battle, and I speak from both sides of the fence as you well know.
I do know sweets. Unfortunate sad truth, yes. I've been in arguments repeatedly over that same thing and not wanting my daughters exposed to that crap. Not when they don't need to be, so it is (in a sad way) better that she is 120 miles away and none of it touches home plate.
Yes... very good indeed. But I also have no doubt that you have the strength of character to handle as best it could be.