The pieces are now moving. Shanks is some kind of antichrist, son of Imu and Garling, a destined child born with a brand who was the destined carrier of Nika fruit. But Shanks chosed to follow his free will and rejected that destiny, he has stolen the fruit and wanted that Ace, the son of Roger receive it but it was Luffy who ate it by accident.

Nami is probably the daughter of Shanks he had to renounce to with regrets, Nami descend from Imu. The point is that everything that Luffy has done is free will, the chosen one is Shanks and failed for good reasons.