How old are the other two siblings does the 10year old get on okay with him if they are older are they kind to him, it would first be good to find out why he behaves like this what triggers the yelling /issues, what happens prior to them as something is upsetting him. Perhaps Mom could take him to the ,Your Mom has to take control crying is no good if anything it makes it worse, your brother need boundaries, if he misebaves the repercussions could be the loss of TV... PC,,,privileges something he minds loosing ,your Mom needs to be consistant in this. Also focus on his positive side and praise him when you and she sees him doing something right. Good Luck,