It's crossdressing.
Let's say that same person made the idea of them starting out crossdressing for a while, going further in their kinks, and end up becoming two trans girls together.
So it'd be both boys' love and girls' love in one story, one couple?
It sounds juicy.
:D
The definition is pretty eye-opening, thanks for the share.
Couple of things. It has already been established that cross-dressing doesn't change the tags for Boys love or Girls love etc. That is a fetish, not a legitimate gender. It does grey the lines, and sexually the interpretation is up to the reader. It can feel more like two girls than boys, or the other way around but people will always have their own perspective and fetishes to imprint on top of the story. So yes, tag it as boys love if both are boys, no matter how feminine they seem.
Almost every transgender person, MtF or FtM has some experience with cross-dressing, but for them it isn't a kink but an exploration into their gender dysphoria and acceptance issues with their own bodies and minds. But this does not mean everyone who tries or likes cross-dressing is trans or anywhere close. There is a big difference between the adrenaline or sexual thrill, and dressing a different way to induce a positive body image. Like Llamadragon said, having a kink for cross-dressing is not something that will normally lead towards transitioning to the opposite gender. Causation and correlation and all that mess.
Cross-dressing may give them a certain mindset and even a yearning for such a thing but it will still remain a fetish. The term transgender is often misused a lot on the internet, in essence it describes a medical condition and not a life-style choice. There are people out there who are boys and love cross-dressing, some even get breast implants, take hormones etc. the whole nine yards. But not all of them are necessarily transgender because of those changes. Even if a large portion probably still are.
Transgender means that there is discord between the mind and the body. This is the same out of place, uncomfortable feeling you get when you know something isn't right. When the world seems wrong or shifted or maybe you have shifted and now feel like you don't belong. Humans yearn to be in harmony with their surroundings, so they will do everything to achieve that, subconsciously or otherwise. For those diagnosed as transgender this discord comes in the form of gender dysphoria. The feeling that your body is not your body, it's wrong. There is something missing, or something that should be there and there is nothing you can do about that feeling each time you are reminded.
The reason people with these kinds of fetishes cross-dress or feminize is for pleasure, satisfaction. The reason transgender people do those things is to stop that voice in their head screaming at them that everything is wrong. It's different for each person and the intensity varies greatly, from people who say they'd kill themselves if they didn't get gender-reassignment surgery to those who think it would be a mistake to do something so drastic. So the idea that cross-dressing can somehow lead people to want to become transgender is pure fetish fuel. Make them want to dress and look and act like the opposite sex, even living as them sure. But that is a lifestyle choice and not a medical condition if gender dysphoria is not present.
Sorry for rambling, I do like the idea of two cute traps together and approve of that. But the trans part really just reeks of cheesy kink fantasy.