How do I get both of my brothers to mature? Quite long, I suppose?

There is probably not much you can do except try to avoid them. They are immature and boys don't mature like girls do. try your best to be compionate but mainly stay out of their way. They will irritate you but self control does wonders. If you see a magazine article about family relationships you might give them a copy of it with a sweet note that says, It seems this is inevitable that we get along at this time but maybe we can also learn from others. Try to play games they like and don't worry if they turn you down. Bring them a cookie or candy once in awhile. don't harp on your brother being fat. He'll figure that one out. Meet friends on your own outside of family and have fun with them. Join in outside activities such as 4 H Club, Scouts, etc.