I been thinking about my turtle gender+sexuality headcanons (the ones I am reasonably familiar with)
Leonardo: I see him as transmasc, most likely coming out in early childhood by simply requesting that his family refer to him as a boy like his brothers, no fanfair. Probably gay, but I can swing bi/panromantic. I like him on the asexual spectrum. He seems most interested in people who can hold their own in a fight, as well as those with some kind of authority. Subby as fuck.
Raphael: Almost stereotypically masculine, you might think Raph is cis, but I see him more as bigender or a transwoman. She is unaware of this, and will never have any kind of egg moment on his own. Needs Donny to literally remind her that Leo transitioned when they were kids. Bi with heavy gay leaning. Wants a partner who can kick his ass.
Donatello: The rare cis turtle, demiromantic or aromantic pan. Sees sex more as a platonic bonding activity, would probably like a qpr.
Michelangelo: My boy hasn't seen a gender she doesn't like, whether that be for identity or dating. Very fluid in how they see both xirself and the world. I do prefer he/him for Mikey, but I also feel that he wouldn't give a fuck what pronouns are used.
Leonardo: I love transfem Leo with my heart and soul (big shock, I know), however this turtle is a veritable playground for identity headcanons. Leo can be read as transfem, transmasc, bigender, agender or really anything you can think of. Will be supremely insecure about this, even when no one else cares. Sexuality wise, Leo is into you as long as you're related to her able to kick her ass.
Raphael: Can be read as either transfem or transmasc, although I'm personally fond of masc. He'd prefer a woman who will kick his ass before pampering him, or a guy he can bully.
Donatello: Donatello desperately wants to be seen as "normal," to the point of refusing to acknowledge that he is both masc nonbinary and bi.
Michelangelo: Once again our pan king, Mikey will fall in love with most people within minutes of meeting them, even if that is very obviously a bad idea. Dtf whenever, but I actually think Mikey would see sex as just a fun thing to do, rather than something to be actively desired. Prefers a more masc identity, although whether that is as a cis guy or trans varies by the day.
Leonardo: A gay transman, big shock I know. Like I don't even think that's a headcanon, I'm pretty sure that's just canon (fight me). I actually think this boy wants an authority figure more than any other Leo, and probably wants to be bullied and praised in equal amounts.
Raphael: I actually see him as cis, but I have seen the transfem art, and see the appeal. Pan as hell, with a preference for the cute and badass. Would probably also like an older partner who could kick his ass.
Donatello: Transmasc nonbinary and living it without shame. Bi, with preference for women.
Michelangelo: "Gender is optional, orange is not" quote stolen from rayshippouuchiha's Naruto Don't Gender Good au. I just think it fits him really well. Ace/aro, but loves the concept of love, just for other people. Arolovic.
I will do Mutant Mayhem after a few rewatches.