Has anyone ever cut off contact with their family?

I have slowly started to consider cutting off contact with my family, with the exception of my uncles and aunts. I usually only see my dad on holidays (he suffers from depression and severly hoards, but cannot admit he has a problem), which is adequate space for me. I moved in with my mom and brother to take care of my mom during metastatic breast cancer chemotherapy (which is over), but living with them in close quarters extremely shows their codependency on each other-I am moving out as soon as my lease is over in April. My mom bases her emotions off of my brother, who is her golden child. My brother cannot hold on to a job, has stolen hundreds of dollars from my mom, totaled her car, failed enough college to be behind two years, and lacks basic hygene skills (using toilet paper and flushing the toilet). His girlfriend keeps a public tumblr about my family, calling my mom the C*** with cancer and writing entries about me being psycho. My mom just keeps hoping he'll change so tries to give him what he wants. He can't function in the real world. When I call her out on that, she will hit me like I am 12 again and cry. I was never treated as well as my brother because I was very shy and overweight, and I spent years in therapy working through my feelings. Now, I realize that their problems are NOT mine. I'm feeling trapped, and I'm only 26. Something's gotta go.