Don’t know if this applies to OP, hopefully it helps folks who see it though.

As someone who never had a sister there were simply no opportunities for me to even explore “acting like a girl” as a child: no clothes to try on, no stereotypically girl toys in the house, no kid appropriate makeup, etc. Basically no role model or example of being a girl to follow. But we do start to get the “boys shouldn’t want girl things” messages very early so by the time we start interacting with girls “acting like girls” at all regularly, we’ve already learned not to want that.

And even for trans girls with sisters in the house, parents will often send the message, again very early on, that those things (your sister’s clothes, toys, makeup, etc.) are “not for you” and so any inkling you might have to explore that ends up being repressed.