Board Thread:Theories and Speculation/@comment-26422608-20150522042352/@comment-5407586-20150523205332

The problem is that Hagoromo commented that what brings forth the Rinnegan isn't Asura+Indra+Sharingan, but just Asura+Indra. Though it's true that the only ones to ever awaken the Rinnegan after Hagoromo were Madara and Sasuke, two Uchiha with Eternal Mangekyō Sharingan.

Not to mention that pretty much Indra=Sharingan.