Here's my answer to the Khan race thing, spread it around if you like it.
Genetics. What a random chance they are! Every birth, every person, is the result of complete chance. Look at your own family - the same parents, yet you and your siblings look different, act different, have different genders. And it's quite conceivable (no pun intended) that in alternate universes, even with your same parents and your same moment of conception, that other you is different.
Okay. Now, consider people that were setting themselves up to be genetic supermen. They are fiddling with genes and eggs and sperm, to improve the human species far beyond anything it currently is. Now combine the chances of conception with full on human intervention, and keeping the mind they are blending the bext genes of humanity... he could have been anything. In the prime universe he was uh, Mexican of Indian descent. In the JJverse, he's Caucasian of Indian descent. In the next universe over, he's he's Khan Inayat Singh, an Eskimo of Indian descent.