But it is in a sense all of those things - you are born with a set of genitals that define your sex, as a result your gender identity is also defined at birth based on the social roles that the society you exist in prescribes. There’s arguably a conversation to be had about the entire concept of gender abolition but that’s a hypothetical that we aren’t anywhere near, for the here and now we have genders and people define what that means for themselves
And if he does, so what? There’s nothing I can do about that so why should I worry?