Board Thread:Theories and Speculation/@comment-25758952-20161108201740/@comment-25122992-20161108203050

I think it was repeatedly implied throughout the series that the markings are the result of the Nine-Tails chakra influence. Naruto, its Jinchuriki, has it, as well as Kin/Gin brothers (who also got its chakra and power) and even Naruto's own children.