I suppose I'm kinda a late bloomer, only realizing I was bi late last year, when I was 23. It's super obvious in retrospect that I was pretty much always bi, but my mind was in other places in my adolescence, namely school and desperately trying to figure my shit out, and then mostly procrastinating reading manga, playing video games, and browsing internet forums, and doing whatever I could to escape from and do the bare minimum of schoolwork necessary to get by in high school. Dating and stuff wasn't anywhere near the surface of my mind at the time, being dominated by all that other stuff. I just new that I seemed to be attracted to women, and that was good enough for me at the time.
However, another key part of my sexual fantasies has always been a sort of fascination with the male form in particular. But the thing is my thing is nonetheless my fantasies tended to focus on imagining having sex with women, whereas the fascination with the male form typically manifested itself in the form of me imagining myself to be all kinds of super muscular and all that stuff, so I pretty much just wrote all that stuff off as just typical male power fantasy stuff at first I guess and didn't think much of it especially since while I wasn't interested in dating in general at the time, I at least felt some girls were cute but didn't really feel that way about any guys (probably due to a combination of bad luck and not really being looking), so I didn't think much of it.
But in hindsight, if anything, I had it kind of backwards if anything. While imagining hot naked ladies did get me going as a teen and that was great, it was always the fascination with the male form in particular and the forms it can take and how attractive it can be that really dominated by attention and got me going, especially at the time (I tend to have a better mix these days that if anything has gone slightly the other way around, especially since I realized I wanted kids more than anything a few years back and kinda ended up developing a pregnancy/impregnation fetish along with that). Looking back on it, it was pretty clear from the beginning that they were anything but power fantasies and it was the male form itself that was getting me going and I don't really know how I came to any other conclusions. Sorry if that doesn't really make sense at all, since I can't really explain it better without going into more detail about what my fantasies actually entailed, which I'm not exactly comfortable with and you probably don't want me to anyway, so just take my word on it on that part.
Whatever the case though, none of this stuff really clicked until I was 23 (probably due to me having a lot of other shit on my mind until then like I said and nowhere close to having my shit figured out until that point and I guess finally being relaxed enough about other aspects of my life to think about this stuff) and just randomly thought about this stuff one day and it just finally clicked and I was baffled that I really ever thought of myself as anything else and why it took so long for me to start thinking of myself at all. It was especially ironic for me since as a young teen, I definitely had an angry atheist phase where I even considered myself an antitheist for a bit (long past all that stupid shit though, thank god) and what was the reason for me becoming such? The area of LGBT rights--something about reading debates about it on the NarutoFan forums when I was a teen just shot off the empathy centers of my brain something fierce, years before I consciously realized I was bi and despite me having a kind of homophobic father. Definitely unusual and I don't quite get it myself, but that's how things went down for me.