You probably were looking at the "Online Members" information. That lists only the members who are currently online and actively browsing the forums... so what that means is that there are 15 members available for Private Messaging AT THAT TIME. There are far more members than that, however. Looks like 7,342 members as of this post...
Anyway, hello there. I'm BlueFusion, I've been a member only a few months, and I'm only 15. There are probably a few people around your age, and there are certainly quite a few people around my age... ABassCube, GameDog2112, Divibisan, BlingBling31k2, and SatanicPopArt, to name a few...