Even though your brother might not actually die, he is certainly in some kind of problem. So, the dream is warning you to watch out for him. He may meet some troublesome circumstances which can wreck a lot of trouble in his life. He might not actually die because sometimes dreams do not mean the same things as that you see. So, what you really need to do is simply advise your brother to be cautious and take all steps carefully. Ask him to be extra careful for a few days such that he can delay the danger that might trouble him soon.