Prior to it actually happening to me, I couldn't really conceive of the possibility.
Now that I have gone through the experience, I can heartily recommend that, while it is very importance to do your best to maintain family relations, it is equally important to protect yourself and the rest of your family from genuinely abusive and/or toxic family members whose only interest in being family has to with what they can get out of you.
I have an uncle who is most definitely a narcissist and possibly even a sociopath. He can be very charming when he wants to be. He isn't physically abusive, but he is manipulative, conniving and ruthless. For years my parents were on good terms with him because they never did anything to challenge him. But when it came to an important family crisis and his interests ran contrary to the wellbeing of our family, his true colours showed.
I now fondly refer to him as "uncle Scar" - a nickname I feel is particularly appropriate since he took me to watch the Lion King when I a boy.