Board Thread:Naruto Discussions/@comment-30168130-20170109030621/@comment-734582-20170112111118

Lorenzo.r.1st wrote: I feel like im that one retarted kid that believes his hillbilly grandpa who says that men never went to the moon It's mostly that the whole senju-uzumaki relation is filled mostly with fanfic and headcanon nowadays. The actual, cold hard facts we have on them are minimal. We know the clans are related somehow. How, we don't know. At the least, we know they share a common ancestor: Ashura. It's not clear if they split from another or from a different precursor clan or something else entirely.

Anyway, I think it's fairly clear that Ashura's clan eventually split into multiple clans, with the Senju being the most direct representatives (essentially inheriting Ashura's beliefs, whereas the other clans went and did their own thing). The Uzumaki did their own thing, including apparently studying Death itself as well as a specific branch of ninjutsu (Sealing jutsu) implying they tried to understand Jinchuriki and Biju. But various people e.g. Kinkaku and Ginkaku and the Raikage have similar abilities to the Uzumaki and Senju, so it's likely that Ashura's people spread across the world and influenced many clans, not just the two we know (and not to such a high degree). We know little of Indra's abilities beyond "he's a genius" and "he has Sharingan", so it's difficult to tell if he has other split off clans.

As to family ties, Mito is an Uzumaki by blood. She's a senju only through marriage. Kushina is an Uzumaki by blood. Kushina is not a Senju, not in any meaningful way at least. Tsunade is a Senju, but apparently not in a meaningful way (She doesn't seem to have strong life or jutsu versatility or wood release, nor the actual clan name). It's not that difficult.