/r/femboymemes is a community of just over 72,000 people. It's what you'd expect being mostly memes, but that hasn't stopped people from posting images and videos of likely underage individuals.
They had a Discord at one point:

That somewhat predictably met its untimely end in dramatic fashion, so one can only image what was on there:
Mod of the sub /u/fingamouse mods exclusively femboy subreddits:

This mod has posted themselves to /r/teenfemboys as recently as 22 days ago and while I can't be sure they're under 18, I definitely believe they are a teen from their posts. A really good way to find these other communities is simply by looking the the mod's and user's profiles and seeing where else they're active.
The reason I mention this is because some of these femboy subs are not obvious at all, for example would you guess that r/TheRatEmpire is filled with young people and femboy/sub content? I sure wouldn't have, but it is!
Speaking of r/TheRatEmpire, they did an age poll about two years ago:

Given the crossover in userbase between communities, it's pretty safe to assume similar results in other subs.
Now about the posting of personal images, there are a lot of posts flaired as
"Not a shitpost or meme" and these are almost exclusively users either posting themselves, or others:


Some of the posters even show their faces and are very obviously young men, with some being confirmably under 18 from their post history. Comments on posts are generally vague and 'affirming', but there's no shortage of creepy stuff if you look.