What is wrong with this person?

Does that sibling have any type of life of their own or are they completely enamored that they are finally being "accepted" into something that makes them feel important? I have an Uncle who is . . . eh, I don't want to say similar but he is a horrible person. He does random background checks on my family to try and dig up information to turn us against each other. He acts like he's been saved by Christ and then proceeds to tell us how we are all horrible people and living our lives in bad ways. He even tried to commission one of my other aunts to kill his sickly mother a few years ago so he could get to his inheritance faster. I've come to the conclusion that people like this are truly miserable. What other reason would they have to cause dismay to others? Normal people don't obsess over trying to hurt other people, especially family members. I would completely ignore those social degenerates and pretend like you aren't related. As for the rouge sibling, I would give them the same treatment even though it's not in the spirit of being a "family" thats certainly what they deserve for deserting you and your family.