You people talking about Madara getting the first's DNA are way off and need to go back and re-read because you missed something. The Sage of 6 paths had two sons, one who received his body and one his eyes. These families are the Senju and the Uchiha, so Uchihas and Senjus share the same blood. This means in a way Naruto and Sasuke are related and it means both the senju and the uchiha clans have amazing techniques that can potentially be unlocked. This also means that if Tobi turns out to be an Uchiha this whole war is nothing more than a family fued that drug the whole world into it.