Family is so stressful?

I've never really understood the greatness of an extended family, and as I get older I am seeing more easily that many of them are cold hearted, selfish people. On my mothers side, she has one sister who is really competitive and arrogant and the other completely disconnected. Her mother makes every problem about herself and is very ungreatful for anything. She always wants to be the center of attention and doesn't really care about others. My dads mother is probably the worst at the moment. First, she's a millionaire. My dad has motor neurone disease now, so he's quadraplegic and terminal within a few years. His mother, in the 2 years he's had it, has never offered the tiniest bit of money to help, and hardly ever helps out with him. She favours her other son and daughter, who are also both millionaires, and visits them all the time and is now living with one of them. That's because he and his wife got divorced and she's the main reason. Uh.. it's very complex and I try to stay out as much as possible but it's driving me insane. She's so heartless. I have quite a few other relatives who are screwed up but those are the main ones. I just don't know what the hell to do anymore!