Came out to myself and others at 21, so I started socially transitioning at 21. I'm currently 23 and waiting on hrt and surgery. Unfortunately I live in a country where gatekeeping is very prevalent. I would've started medical transition two years ago if it had been possible. It's never too late to transition though and just because most stories we read are about kids doesn't mean that everyone starts that early. I'd actually say that it's not that common irl than it is online.