What if Naruto when his father Namikaze Minato sealed the Kyuubi inside him the stress on his body and mind from being that close to Kyuubi and having it sealed inside him made his Rinnegan activate temporarily and let him assimilate his fathers dead body and sooner use it.
Then his bloodline went inactive again untill he was attacked by some shinobi when he was some where between 4-8 years old, he managed to use his fathers body and abilities to kill the shinobi who should have some kind of bloodline, Naruto then uses his fathers knowledge to train himself.
Anything else is up to whoever if someone wants to write this story,