Since 5, everytime my brother makes too much effort, in the evening he gets terrible leg bone aches that even wake him up! why? what's wrong with him?

Growth spurt: If your brother is going through a growth spurt the bones grow faster then the muscles so the muscles are a little too short to work well. They are then overworked and at night they cramp up and cause pain. This condition usually corrects itself as the muscles get longer with normal growth. Please have him checked by his Pediatrician to make sure that he is OK and that this is normal for him.