Trans people: at what age did you start taking hormones?

I came out to my parents as transgender when I was about 15 (or rather I was forced to) and pretty much nothing has changed since then, except my main psychiatrist, -who's quite transphobic, luckily I'm leaving her in a few months- has once mentioned me hormone therapy. I couldn't stop thinking about it ever since, I had no idea I could do that and I felt so hopeful- but my parents are still not accepting and that doctor will not allow me to start any kind of treatment until I "cured" my depression. Long story short, I can't take hormones until I'm done with high school, so until I'm 19, then it won't be possible to start the therapy in about two years or so (and the medical centre is two hours away, the train is a bit expensive, so the whole thing is simply out of reach).
I know it's never too late to start transitioning, and 21 doesn't sound like a bad age to start ofc, but it feels like I'm wasting my life every single minute I spend in this suffocating body, you know the feeling, right? Plus, I know SO MANY trans people who started HRT at around 14 or 15, and it saddens me knowing I could've done that. I just want to know what the most common age to start is.