Yep, its merely awakened by Indra and Ashura Chakra. If Hahsirama had taken some of Madara's DNA, he would have awakened the Rennigan as well. Even if some random nobody took DNA from Madara and Hashirama, it would probably still allow them to gain Rennigan.Well true the Uchiha wouldn't able to achieve The rinnegan alone without Senju DNA which makes this dojutsu its own form nvm about the Byakugan I was basing on.