We all saw that Madara awakened the Rinnegan just before his prolonged death . If i remember well he said that for an Uchiha to awaken the rinnegan , you must have senju DNA. Obito can have and control the Rinnegan because he has both Uchiha and Senju DNA . Nagato on the other hand could control the Rinnegan because he was an Uzumaki . Uzumaki clan is said to be a clan relative to Senju clan , but that would also make them relative to the Uchiha. Moreover i believe that The Uzumaki is not a relative clan but the parent clan . i strongly believe that Rikoudo Sennin was an Uzumaki . i know that this was said before but now it seems that it will soon be revealed . Strong life force , stamina , longevity , specialty in fuinjutsu and the rinnegan . what do you guys think ?