They aren't descendants of Indra or Ashura.
Isn't that racist? Ashura isn't racist
:| Why can't a Senju manifest the Sharingan? I suppose that's racist too?
That's pure genetics my friend.
I know that, same principles apply to this. Naruto's and Sasuke's genetics make Ashura and Indra their ancestors hence the transmigration cycle.
Nah, the two only chose those related to them as well as two who were in conflict with each other. Genetics has nothing to do with it.