Board Thread:Theories and Speculation/@comment-33485854-20180625233306/@comment-33485854-20180630132039

Sasuke got the Rinnegan due to Hashirama's chakra (and cells?) being gifted to him, giving him Ashura's Chakra and compleating Hagoromo's Chakra.

When Hagoromo granted him Six Paths Yin Power he activated the merging of Chakra and Sasuke awoke his unique Rinnegan.

I also assume Hagoromo also just gave Naruto Six Paths Yang power, so he wouldn't awaken the rinnegan, and giving him the ability use Six Paths Senjutsu, however the process works. (A question I made this thread for)