Im scared of my brother?

i have read about other girls cases and they are much worse than mine but my brother still shouts at me and hits me 'HARD' he is currently sleeping after hitting me and i decided to see if other people had the same problems. I hit him back sometimes, which ino is wrong, and he always ends up hitting me ten times harder he is in year 9 and im in year 7 , the year i suppose an older sibling should support you, and hes been hitting me since i was about 6 gradually hes hit me harder and has got more agressive my mother and grandmother are scared of him so they dont say much even though they defend me as much as they can most of the time they say im as bad as him but they dont realise that im younger and weaker. My mum split up with my father recently and we are living at my nanas in a small flat with 2 bedrooms so it has became even more stressfull, he calls me a retard and a special child which annoys me and starts the whole thing. I dont want to phone the policeor anything because he is my brother and i dont think that he has anger issues because he only hits ME i suppose he thinks this is ok because hes done it for quite sometime but im worried incase this gets out of hand and hurts a girlfriend/wife laterin life hes a nice person to other people just not me. He cant even be nice with me if i see him in school he pushes me away and slaps me on the face it embarrases me and frightens me what should i do?