Not everyone will be perfect in every aspect of the game. I am pretty sure gretzky could barely even do a chin-up
One big thing that players should learn is to play to their strengths, yes he should work on being a great all around player, but while he is on the ice, make sure he does what he does best. Work on weak points during practice.
As a younger player I was always the smallest guy on my team (I didn't fill out until about 17 - 18) I was quick, so I tried to skate by as many players as I could, instead of knocking them all over, or stickhandling around each player.
Also for throwing hits I learned how to throw a mean hip check and took out some players that were much bigger than me (not to often through for fear of retaliation)
I was a pest in front of the net, and I was little. You and your brother can practice this together, get a stick each and one ball and play keep away in a small area, the idea is for him to learn to protect the puck and use his body to block you and push you away.
After a while he will learn that if he widens his stance, and positions his weight properly, he will get an advantage over other players who are even bigger then him. It looks great if a small player who knows how to use his weight can displace bigger players who are not confident on skates.
I hope that helps