Bitcoins have been over a couple of hundred dollars for more than 5 years now. Kids can only get so many by mining. Don't imagine too many teenagers have 10+ bitcoins without family help in getting them.
Bitcoin is maturing, and so are its holders.
Alts are probably a different story
I think people with most bitcoins are on the range of late 20s to 30s because the youngster nowadays can catch up to the oldies especially in terms of technology advancement. The most bitcoins holder cannot be seen in age as long as you manage well your coins and keep on engaging and studying it you have a potential to possess more of it.