Trans people aside, there are people who are purely biologically not XY-male or XX-female. You can have X, Y, YY, XYY, XXY, and XXYY. And more, but the further you get from a pair, the lower the viability. Not to mention things like hormone insensitivity, where you may not develop primary or secondary sexual characteristics, or having sensitivity and developing too much in a certain way.
It’s all very complicated, and honestly when it doesn’t affect me I don’t worry about it. Let people live their lives the way they want in peace and everyone will be much happier.