Help with brother!!!?

Okay I'm 15 and my little brother is 11, lately (the last 3 months) he has been so annoying... Okay for instance today I told him to make sure to hold our guitar with one hand on the neck and one on the body so he wouldn't break it. He goes down stairs tells my mom that I am controlling/bossing his life. WTF??? This happens everyday if I'm like hey do you want to throw a football he's like mom CJ called me fat... Me- mom I asked if he wanted to play football?? Mom- okay both of you stop arguing???? Is my brother just annoying or will this pass? And what do I say to him so that I don't get in trouble??? Thanks CJ!