Is trying to gain 10 lb. a week healthy?

My brother is 14 years old, 5 feet 9 inches tall, and cheerily weighs 162 lb. of mostly muscle. He had a goal of trying to gain 10 pounds a week, since he plays ice hockey, and has started complaining that he isn't really gaining anything, despite how much he eats and works out. Is this normal, and is there anything he can do to increase his weight gain?