Just coming out of left-field here, but could be due to Varicocele, which I'm surprised isn't really mentioned on this board since it's very common in adolescent males and men.
http://en.wikipedia.org/wiki/Varicocele
If so there are new surgeries which are apparently very successful. The younger one gets it seen to the better.
http://en.wikipedia.org/wiki/Varicocele
If so there are new surgeries which are apparently very successful. The younger one gets it seen to the better.