The True Relationship Of The Uzumakis To The Senjus And Uchihas
Others insist that the Uzumaki Clan descended from the Younger Son, this is simply not true, one of the simplest reasons they couldn't is the Clan's trademark red hair.
We have here the Younger Son who clearly doesn't have red hair, in fact if we look at the anime depiction, the hair color is black:
And his descendants (Hashirama, Tsunade, Tobirama, Nawaki,etc.) didn't have red hair:
Then suddenly there's a "descendant" clan (Uzumaki) of the Younger Son whose pure blooded members (Naruto is half) all have red hair??? doesn't make sense. Obviously the Uzumakis like ancient clans practice "inbreeding" that they have always had red hair:
(Pure Blooded Uzumakis)
Taking Biology into account, hair is one of the most consistent genes, and having the same color of hair in a clan who inbreeds is true. It doesn't make sense that a "descending" clan could develop such an unorthodox hair color if the original hair color was a different color. The interbreeding clan (Senju) would have to have red hair, or a strong dominant gene for it, but the Senjus don't, and red hair in itself is a recessive gene in humans.
Another thing is the place of origin of the Uzumakis: The Land of Eddys.
(Red Square is Uzushiogakure)
If they were a descendant clan of the Younger Son, then why do they live in another country? The Senjus and Uchihas' origins have always been in the Land of Fire even before the foundation of Konoha:
Not to mention the Uzumaki Clan's non-participation in the First Shinobi World War:
The Uzumaki's absence and apathy to the war indicates distant blood relationships. not close blood relationships with the Senjus.
In fact, the Uzumakis weren't even the first ones who joined the village:
It's because they only have distant ties with the Senjus, not to mention they lived in a whole different country.
Thus proving Kushina's statement that they were only distant blood relatives:
And let's think about this logically: If the Uzumakis descended from the Younger Son, then they would be a "sibling clan" to the Senjus, and two sibling clans who share the same common ancestor would be considered a close relative not distant.
Lastly, we need only to look at the history/inspiration behind the Uzumaki Symbol:
The Spiral Symbolism is one of the most ancient (if not the most ancient) spiritual symbol known to man. Dating back to the prehistoric era.
(The Triple Spiral: Ancient Symbols dating back to the Megalithic and Neolithic Era)
And since the Uzumaki Village is known as the Village of Longevity:
Then it only stands to reason that the Uzumakis are older than both Senjus and Uchihas.
The Uzumaki Clan therefore are not descendants of the Younger Son, but a cousin clan to both Senjus and Uchihas.
You may ask then if there really is a relationship between the Uzumakis and the Uchihas?
The Uchiha Tablet was used with the Uzumaki Shrine Mask to unseal the Uzumaki Shiki Fuujin.
The Uzumakis are cousins to both Senjus and Uchihas.
The Senjus and Uchihas descended from Rikudou Sennin:
The Uzumaki Clan descended not from Rikudou Sennin, but from Rikudou's Uzumaki Relatives.
Rikudou himself coming from the Uzumaki heritage:
Thus making the Uzumakis a distant blood relative to both Senju and Uchiha as a cousin clan.
The Rinnegan came from the Juubi:
That is why only the combination of the DNA of the direct descendants of Rikudou Sennin: The Uchihas and Senjus, could awaken the Rinnegan, because they have the Juubi's essence inside them.
The Uzumakis do not have the Juubi's essence, that is why they couldnt awaken the Rinnegan, they only have the immense Vitality, Chakra and Sealing Techs that Rikudou Sennin had prior to becoming the Juubi's Jinchuuriki.
The formula then is:
Uzumaki(Rikudou) + Juubi = Senju and Uchiha