More body hair is a sign of higher testosterone... guess your son has more "man-hormone" than those other little boys.
lol! So funny....my DH can't grow hair to save his life!!! He is 26 & doesn't have a single hair on his chest!!
When he was 16 he was paranoid too, coz he was the only one without hair under his arms!!
Sorry I'm not much help, just letting you know it works the other way too.