Board Thread:Theories and Speculation/@comment-24824859-20160108012905/@comment-26369387-20160108021135

I agree with Omnibender, common ancestors would make sense. And I think who those would be: Ashura, Indra and child/children of Hamura that stayed on Earth.

Now, hear me out. As we know, ancestor of Senju clan is Ashura and ancestor of Uchiha clan is Indra. But what if A and I had both several children and Senju and Uchiha are not the only clans that have descended from the A and I? It has been said that Kingaku and Ginkaku are distantly related to Hagoromo, so it's not impossible that they're related to him through Ashura or Indra(although Ashura is more likely).

As for elemental kekkei genkai shared by several villages, let's look at Lava Release. It's shown to be in three villages: Cloud(Dodai), Rock(Kurotsuchi) and Mist(Mei). What if one of Ashura's descendents had Lava Release and when HE/SHE got three children, each of them getting Lava Release, seperated for some reason and each of them moved to areas that would become Cloud, Rock and Mist in the future?

The "poaching" IS possible, too.