My mother verbally abuses me and my father and hits him what should I do?

She's never hit me or my brother and sister but she hits my dad and verbally abuses me I'm only 12 I don't know what to do help please! She almost broke my dad's wrists they fight a lot she has PDD but I don't think I can live like this any longer it's making have suicidal thoughts because she has convinced me I'm worthless and she grabs my writs REALLY hard so there's marks. I'm scared.