why does someone act like that?

I want to know why someone acts hatefull toward thier child because the child is learning and only 10 yrs old. Someone that seems to be always mad at the world doent deserve a child or even to be around me. The person I am talking about is my own brother which is 36 yrs old and one lazy person. He doesnt like the four letter...WORK!!! With that said he is always worried about baseball which he coaches or watching foorball on t.v. Life is more improtant than both of those and I feel that if he doesnt want to grow up or act right then dont be mad at the world all the time.