Kaguya Other Son Power ?

[Seventh Sama]

I think the brother got kaguya's byakugan and a strong body/lifeforce. He might've been something like neji but with larger chakra reserves and possibly was a sage mode user...

Think about it this way:

He isn't related to the Uzumaki, the Uzumaki are a pointless fodder clan, No one cares about the Uzumaki except naruto fanboys who want to turn him into the Sage, even though that theory has been throughly Killed.

Oh so a clan that can handle both rinnegans(i.e nagato) is useless? Even obito whose half senju and uchiha can barely handle one :|
There's something special about them....