Are my parents normal?

my mother has always been very controlling and never allowed me to go or do anything unless there was no way around it. My stepdad is childish and sulks when he doesn't get his way. We are moving soon and my sister, who was 17 at the time but is now 18, stood up to them and said she wasn't going to move all the way across the country. They responded by putting her in Brentwood, which is a mental hospital for her "behavioral issues". She was there for a month and pretended to agree with them so she could get out. She turned 18 shortly after and moved in with my aunt and uncle to get away. Now I'm terrified to disagree with them because I now know they can legally throw me in a mental hospital anytime they want. My step dad is horrible to my stepbrother. He's slapped him in the face and grabbed the back of his kneck and hair to drag him. I understand that this isn't physical abuse though. My mother hates my grandparents, whom I'm close with, and does everything she can to prevent me from seeing them. Every opinion I express that is contrary to their own is mocked and looked down upon. I look at my friends parents and I don't see anything close to this behavior. Is this normally how families are?