Saying it is biologically impossible to change sexes misrepresents the issue. A transgender man can not currently be 100% biologically male but saying a transgender man is 0% biologically male is highly inaccurate. There is incredible power in suppressing one sex hormone and replacing it with another. In the womb, hormones decide gender, not chromosomes (some people have XX chromosomes and are born male). If these hormones are responsible for gender inside the womb, can't they be considered to change gender outside of it?

The face, chest, voice, decreased libido, reduced muscle mass, and redistributed body fat of a trans woman are biologically female. The face, voice, increased libido, muscles, body hair, increased weight, and increased appetite a trans man have are biologically male. And of course a trans man and woman both look indistinguishable from other men and women. I would say a transgender person can have 85% of the things the opposite sex has, and none of the things they are missing should prevent them from being considered as the opposite sex. Just because someone can't reproduce doesn't mean we no longer define them as their gender anymore, so that standard is ridiculous when applied to transgender people.

Please look at my examples of a completed transition again.