Board Thread:Theories and Speculation/@comment-3965545-20160511191323/@comment-734582-20160512085908

Omnibender wrote: I've always been critical of the lack of clarity on the whole Senju/Uzumaki relationship. We know they're "cousins", but there has never been a clear indication of how. Simple. Ashura had a bunch of otsutsuki kids who had Otsutsuki kids and somewhere along the way, those descendants became Uzumaki and Senju. Similar with Indra. His kids weren't Uchiha, they were Otsutsuki. Somewhere along the way they became Uchiha. Both probably because they mingled with humans. The Senju were the people who simply inherited the Sage's body the strongest.

Besides, since the Senju clan contributed heavily to Konoha, there are good odds many Konoha citizens have at least some part Senju in them.

Seelentau wrote: err, every Uzumaki is part of the Senju lineage, simply because the Uzumaki stems from the Senju clan. (that doesn't mean that we add every Uzumaki as a Senju, though. They're still two separate clans) This isn't true. The Manga never says this.

Nagato is an Uzumaki primarily. And since the Senju and Uzumaki were friends, it's not rare they would have mixed kids (hell, hashirama's kids would be exactly that). Being part of a clan that has extreme lifeforce and part of a clan with the Sage's body, of course Nagato would be extremely fit for the Rinnegan.

Just like Hashirama's children, Nagato alone isn't proof that the Uzumaki stem from the Senju. Hell, Hashirama's children prove the exact opposite.

So yea, OP is correct. Nagato's situation could be as simple as a Senju moving to the Hidden Eddy, marrying an Uzumaki, and then after it's destruction flee to the Hidden Rain.