Why doesn't my brother get in trouble?

Okay I am 13 and my brother is 11. We were watching a movie and as he came back in from getting a snacks, he called me an a hole. No reason. Anyways, he hands me the plate later left over from the snack and no manners what so ever says, put it beside you, you have more room. I ask him to say please and he just tells me to shut up. 5 minutes later and a few swear words pointed at me, I ask him to get out. He says no and I say its my room. So, he says. I finally close the laptop we were watching the movie on after 4 consecutive tries from him to push the space bar and make the movie play. We bicker until he punches my arm. He wouldn't stop and punched about five times. I mean it didn't hurt but I am scared when he is going to be bigger than me. He already is 110 pounds. SO I just went downstairs because my mom called me to come pick up my school supplies. I go downstairs and say, ha ha you didn't get a chocolate bar. He gets away with everything and my parents dont care when I tell them. They even believe me and still dont!!! Please help me to handle this madnessss!