OT - short boys

My son (oldest boy with 4 sisters, poor kid), just turned 10. He is not going to be a tall boy. He just recently started wearing size 7 pants. He is Hispanic. Bio dad, we are guessing is around 5'4"-5'5". Bio mom is slightly taller at about 5'5"-5'6". Both of his younger sisters (full bio) are taller than he is. For awhile they were all three at the same height, but he just hasn't grown like they have. He still shows enough growth on the chart that the Dr isn't concerned...he's just going to be short! He also has a metabolism that doesn't stop! He eats like a teenager, yet skinny as a rail! He sometimes gets self conscious about it...especially when someone thinks he's only 5 or 6...but he has a great sense of humor, so it doesn't get him too down.