Here's another question. How young is too young to start? May look to get my kid brother into it as well. He's 12.
Maybe think about getting him involved in a club?
I love cycling and my interest in it has morphed from the competitive road cycling (never raced formally but drilled myself every time I got on the bike) to a more expansive vision of where my bike can take me and what tools are needed to achieve it.
One thing that strikes me is that for "road" cycling, it's definitely more fun with other people. Spending hours grilling on a road with cars buzzing you isn't for everyone, and probably even less so for a youngster. Track, cyclocross, MTB etc might be good entry drugs for the young dude.
I'm riding a "monster cross" bike at the moment and loving the versatility. It's a steel beast and has braze-ons for racks, fenders and the like. Fits 2.1 inch tires (i.e. fucking massive amounts of rubber if I want it) and has the option of altering geometry. It means I can comfortably commute, ride on tarmac or take it down some rutted goat tracks.
I've just bought some bags for a camping trip over the Dargo Road in Victoria's high plains. You could possibly do it on a road bike, but it'd be a bit hairy and you couldn't carry the gear.
Moral of the story? You don't need to follow the lycra crowd (not that there's anything wrong with them!) to enjoy cycling in all of its forms.