If you are interested in a person you assume to be cis, and they have had bottom surgery so the only real way to tell if they are trans is if they tell you, and finding that out makes you decide against having sex with them, you're a transphobe.
If you are interested in a person who is trans but has not had bottom surgery, and that makes you not want to have sex with them because you are not attracted to penises/vaginas/etc., you are not a transphobic
not really. "mate" and "raise offspring" are basic drives but they're just rough heuristics that approximate "pass on your genes". animals raise young that aren't their own, even of different species, all the time. different human societies have had vastly varying concepts of who raises which kids - many would raise kids communally, without regard for who the parents were. taking our societal notions about "passing down your genes" and making evopsych arguments for why they represent "human nature" is just laundering the present into the past and pretending that this is the way things have always been.