From the begining of school to now i have put on 15 pounds all muscle. I have always eaten like crazy but in a healthy way similar to what swampboy was saying. Protine shakes in the morning do nothing but make your urine more expensive. you are not using the protine so there is no use taking in that much. Maybe a bar or something but shakes seem almost wasteful. shakes after a workout is what is useful because your body actually needs the amino acids and protines to rebuild your body.
Lots of carbs too and i don't mean mcdonalds or twinkeys. I'm talking apples, oatmeal, bread and grains, healthy cereal thats high in carbs, and other things that are hearty and make sure to mix simple and complex carbs.
Also remember you can lead a horse to water but you can't make it drink. If his body won't gain weight, then just let him be stronger. I know we all want a guy who is 6'0 200lbs but some guys aren't built like that. I didn't start gaining weight until i was a sophomore and now being a junior it isn't as hard as before. I burn everything and am skinny but i put on muscle pretty easily now. just do everything within your control and thats the most you can do.
hope this helps