What your describing in this family member could be called something like - vampire personality.
People of this kind could be anyone.
Could be a boss, a wife, boyfriend, anybody.
More than not they seem perfectly normal but there is a hidden side where they will slyly try to suck the life out of those around them.
One of the ultimate goals is to break up families.
I personally know of a guy who's wife was like this. After twenty years or so the guys own mother disowned him, and considers he doesn't exist. His wife was the source of it all.
Still incredible to me that she brought to that point.