Well if you want to discuss why he is born with whiskers it would be a completely different topic, and that has been done before though it has never been proven, besides since there are 6 whiskers I'm gonna go with the explanation that it is because he is somehow related or born with some of the sages genes, and I believe it would be the genes of conversations. SO6P was also a savior because everybody liked him, cause if not it wouldn't be possible anyway.
Kinkaku Ginkaku probably just had strong chakra and were raging psychopaths after the kyubi swallowed them. I believe that Kishi showing whiskers on them and raikage saying his wise words, backs this up more than it would be the jinchuriki. Think about it. Mito also gave birth, and most likely after having kurama sealed, since how else would anyone know about the weakened seal during child birth? We don't see anybody in her family with whiskers. Also why would Kushina let the 9 tails chakra influence her baby? That would probably be the last thing she would do..
Don't forget I said they might be related to uzumaki, might just be a distant relationship.