This is an issue of communication. If he is living in the same house but refuses to speak to you, try your level best to make a statement to him that if you don’t know what is making him angry, you can’t fix it or change it! He must tell you of your mistakes so that you may change them or defend yourself. If he still refuses, ignore him for few weeks and then call your parents or his parents and complain to them so that they can come and talk to him about this childish behavior.