Board Thread:Theories and Speculation/@comment-1872728-20160229033316/@comment-734582-20160301221730

Georgio722 wrote: Well, the Kaku Brothers are distantly related to Hagoromo Loads of people are distantly related to Hagoromo. It's not exactly a rare thing. As to Uchiha/Senju, it's not clear when or why the otsutsuki name died out. It seems that the "kekkei genkai" of the Senju and Uchiha was well-preserved by these clans. It's possible other clans that originated from the Otsutsuki were less concerned with their genetics. or they simply died out (like the Kaguya clan).

As to the Uzumaki, they likely originate from a bunch of Senju that broke off from the original clan and formed their own, and through intermingling their abilities changed to what we now know.

Thus, it's not exactly clear how many clans branched off from Indra and Ashura Otsutsuki. Only that the Uchiha and Senju have the purest respective powers.