Sage of the 6 paths/uzumaki
I didnt believe it @ first, but thinking abt it some more i came up with a theory.
yes the SO6P may have been a Uzumaki(originally)....
his two son would be related to the Uzumaki as well, but since the Senju(younger son) inherited his strong life force and body their closer related to the uzumaki then the uchiha...
the uchiha and senju are already distantly related, since their ancestors are brothers....
it would make more sense, since naruto is the reincarnation of the So6P, being from the same clan!