Life has its difficult questions and unusual cases but so what; those are not your circumstances and therefore you are not justified in them. Using that to ignore or, worst yet, justify foolishness on behalf of the overwhelming vast majority who have not the need to face such questions with regard to themselves is akin to mindlessly grasping at straws.
Mankind can and does mutate just about everything it touches, religion by decree and the physical world by action. Physical deformity is causal in mortality and has nothing to do with the commandments of God with regard to gender pair matching. The reality is that life, trial, growth, and progression does not begin with mortal conception nor does it end with death. No one is held accountable for not being able to conform to commandments that they are incapable of conforming too and those whom you speak about will have opportunity to choose and justice done to them as we all will. The bottom line is that pointing to others to justify yourself doesn't work. When you stand before God to be judged you will not stand there as anyones spouse or son or friend; you will not stand as a rich man or a poor man, a scholar or a dummy; you will stand there as a son of God stripped of all your excuses for sin. I firmly believe that in that instance, if you are not worthy of the atoning intervention of Christ on your behalf then...well...lets just say you will not be a happy camper.