Yeah, we all know the story of the sage of six paths having two sons - the Uchiha guy and the Senju guy, but guess what - it was told by Obito, and we all know how good he is at telling lies.
My theory of the making of the great clans goes like this:
The sage was an ordinary human being, but that doesn't mean he didn't have some "spiritual power", like shamans, which I think was canaled trough his " weapons " like magic is canaled trough a wand:
So, after he defeated the Juubi I believe the sage sealed off the tomoes (which represent 'evil') via "spirit powers" and made rinnengan. He also gained chakra which made him the first ninja and enabled him to use techniques such as izanagi which is a technique made for creating things:
I believe that he used this to create his two "sons" the Senju and the Hyuuga (I mean his dojutsu looks more like byakugan doesn't it? And they have MENTAL ENERGY - which the Uchiha don't have obviously!)
~But, what about the Uchiha and the Uzumaki?
In my opinion, the sage was an Uzumaki (because you can't have ginger offspring if your hair is black, and it's possible the other way around) and I believe he had a child older than his "izanagi sons" who he had made before he become a jinjuriki leaving that child with the "spiritual powers" which he/she has learned to canal like the chakra of the Senju's, which can be the reason of them being called Senjus 'distant relatives' (and let me also remind you that it was never denied that Uzumakis weren't also related to Hyuugas or Uchihas).
When it comes to Uchiha clan I belive it truly is a Hyuugas branch, and that it was created with the help of the Uzumaki clan. The thing which lead to it may be that, due to much incest in Hyuuga clan, a mad ear was born and in despair the elders spoke to the Uzumaki's asking for them to preform a seal to put his/her emotions away and Uzumakis couldn't think of anything else but the tomoes which they were given to protect by the so6p.
My theory of the making of the great clans goes like this:
The sage was an ordinary human being, but that doesn't mean he didn't have some "spiritual power", like shamans, which I think was canaled trough his " weapons " like magic is canaled trough a wand:
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So, after he defeated the Juubi I believe the sage sealed off the tomoes (which represent 'evil') via "spirit powers" and made rinnengan. He also gained chakra which made him the first ninja and enabled him to use techniques such as izanagi which is a technique made for creating things:
You must be registered for see images
I believe that he used this to create his two "sons" the Senju and the Hyuuga (I mean his dojutsu looks more like byakugan doesn't it? And they have MENTAL ENERGY - which the Uchiha don't have obviously!)
You must be registered for see images
~But, what about the Uchiha and the Uzumaki?
In my opinion, the sage was an Uzumaki (because you can't have ginger offspring if your hair is black, and it's possible the other way around) and I believe he had a child older than his "izanagi sons" who he had made before he become a jinjuriki leaving that child with the "spiritual powers" which he/she has learned to canal like the chakra of the Senju's, which can be the reason of them being called Senjus 'distant relatives' (and let me also remind you that it was never denied that Uzumakis weren't also related to Hyuugas or Uchihas).
When it comes to Uchiha clan I belive it truly is a Hyuugas branch, and that it was created with the help of the Uzumaki clan. The thing which lead to it may be that, due to much incest in Hyuuga clan, a mad ear was born and in despair the elders spoke to the Uzumaki's asking for them to preform a seal to put his/her emotions away and Uzumakis couldn't think of anything else but the tomoes which they were given to protect by the so6p.