My sister's brother is a psychopath.

Did I tell you guys that the guy who is according to the law my brother molests me? I think he's a psychopath. I just didn't want to lend him my PC and he got really angry and he grabbed my throat and pushed me against the wall. He threatened to punch me and my boyfriend's teeth out and beat us into the hospital.
Last time I refused to lend him my PC he deceived me with a knife. But like a huge knife 30cm or something, but I'm a stubborn person and I didn't bow for him.
When I was 9 I got suicidal because of him, because he kept beating me till I lay crying in the corner begging him to stop. He only did this when my mom wasn't home. When I was 13  was still suicidal because of him and then I got another hit. My at that time best friend told me (no she didn't tell me she showed me clearly enough) that she didn't want to be my friend anymore. When I look at it right now I'm happy that I'm not her friend anymore she became a real vegetarian bitch. And before she stopped being my friend she treated me wrong anyway. A few months and many suicide attempts later I met Sam, my boyfriend and he helped me get over it, and get over thinking that my brother should always be forgiven. He made me happier than I had been in years. And I'm always happy now, happier then I ever was, but it all changes when I see my brother. Then I become so depressed, all I want to do is get rid of him, I want him gone. The day I have enough money to move out, I'm moving out right away. I'm already saving for it now.
seriously the day he becomes 18 I'm going to sue him. I looked it up and if I win the trial in court he has to get to prison for at least 6 years.
I know he's not worth wasting time on, but he needs to get punished for what he does. My mom always says that he does that because he used to get beaten by his father when he was a kid when he didn't play well enough at soccer. As if that makes everything all right. As if I will think then "Oh, that's the reason. Come on Arno beat me to death, it's all right, I love being beaten if it's for that reason." I know that he's her son and that she wants to protect him and see all the good in him, but I'm her daughter  and I actually need the protection. She acts like what he does is not a big deal, but to me it is. He's a monster and he needs to suffer. When he dies I'm going to spit on his grave.

EDIT: I talked to my father about it and he thinks that Arno is right