Well regarding your recent sighting, most likely, all of the boys smoke. The one you saw smoking probably started with the others, who were already smokers. Since he likely started with their support and encouragement, "coming out" as a smoker to his friends probably wasn't an issue. But, for those of us who started on our own or with older siblings, its an interesting question.
I started on my own at 12. I knew i liked it right away (even before I figured out how to inhale) and that I'd keep at it. Although I knew some kids from school who were already "experimenting" with it, none of them were really friends of mine. So, I continued on my own for 8 or 9 months as I had the chance. But by then, I really wanted to share my new hobby with a friend.
My best friend at the time had 2 smoking parents like I did and also had an older brother (about 15 at the time) who already smoked openly. So, I figured he'd probably at least tried it by then and even if he hadn't, he wouldn't be opposed to the idea. But rather than tell him I smoked or ask him if he did, I came up with a plan.
Before meeting up with him one day, I stashed the pack I had in the woods where we hung out. Later when we were there together, I happened to "find" that pack which someone had apparently dropped. Conveniently, I "happened" to have matches with me. With the "found" pack in hand I asked him if he wanted to try one. Not surprisingly, he said he would. So we each lit one up and admitted to each other that we'd both been sneaking them on our own for a while. Since at the time, cigarettes were relatively cheap and easy to acquire, even for 12 year olds, smoking together became a daily activity for us. Within a month or so, we'd invited another friend who was a year younger than us to join us.