Well, scientifically there is no meaningful distinction between gender and sex, and while there are non-binary states of sex (as a result of aberrations) there are no genders outside of that group.

Gender expression varies significantly, but it’s entirely irrelevant since it’s arbitrary, one person’s skirt is another one’s kilt. Simply put, a boy can wear braids, lipstick and like to bake cookies, but it doesn’t make him any less of a boy.