Hey why does my brother call my mom retarded? How come he doesnt get punishment?

When I am mean to my brother, I'm always the blame because he backfires me all the time. He's insanely rude and obnoxious. He is quite clever with his words. So I'm the one who is always in his trap. He doesn't give a frick bout what he does to me. He only cares for a reaction. Yesterday, my brother threw a beach ball in my face for no apparent reason. I wear gles and if my lens broke and it gets in my eyes I could be really hurt. Yeah, he didn't apologize and my mom said I was over sensitive. Yeah, well I didn't know he was that stupid to throw something right in meh face. He always calls me a stupid fat a s s retard. It hurts. Who is there to help? I feel like this needs to be a end to this catastrophe. I'm really having a meltdown. I hate being called names such as b word and fatty. Retard is not acceptable.