@literall45-- You might want to see his pediatrician to make sure that there aren't any underlying health conditions. If not, then don't worry about it. This is actually an age range where children experience different growth rates. Some grow faster than others, and girls usually are taller at this age. It's highly possible that your son will experience a growth spurt sometime soon.
You can encourage him to be more active and play sports. All sports are beneficial for physical development, it doesn't have to be basketball, it can be baseball, soccer, martial arts, even dancing.
What's probably more important than his physical development right now is his emotional state, especially if he's feeling self-conscious about his height and size. Make sure he knows that he still has a long time to grow and he will probably pass all his peers soon.
My son was also a late bloomer, he was shorter than everyone else until he was ten and then had an immense growth spurt and passed everyone else. He was feeling down about it for a while though and I did all I can to make sure he felt better. Once, I even shortened his pants overnight to make him feel that he had grown the next morning. He was so happy!