@puppygirlhornypost2 to kind of take over here for you (because this is a topic that I've thought a decent bit about):

transfems are likely to come from backgrounds where we're either estranged from our families entirely, or have strained relationships with them. that's why we tend to gravitate so hard toward found family and developing emotional intimacy with one another. (and like, none of this is unique to transfems - we'll find some measure of this phenomenon throughout the broader queer community - but since we're talking about this with regard to transfems, I'm singling us out here.)

sometimes, in doing so, we tend to develop feelings for one another that are both familial and sexual/romantic. these feelings might already be tangled together in our heads - fauxcest is often little more than desire to have a loving, supportive family that's been sublimated through kink - and sometimes they become entwined along the way.

thus, we often find girls and enbies in our communities calling each other "mommy," "sister," "daughter," etc, hand-in-hand with a relationship that's sexual, romantic, or both.

of course none of this in any way resembles actual incest - it's just sublimated kink and found-family tropes playing out in dramatic little ways throughout our interpersonal relationships. but to outsiders who aren't aware of that background, or to other queer people who don't feel the pull toward relationships of that nature, it might look like the other, far more taboo thing.

there's also elements of transmisogyny (the idea of transfems as predators) and specifically the intersection of ageism with transmisogyny (the idea of older transfems, specifically, as people preying on younger transfems) interwoven into that tapestry, but those would take me much longer to write about 😅