Don't read if u haven't watched anime up to ep. 460
! I just watched ep.460 where Ace 's bloodline is revealed & here 's what came to mind.. I think Garp might have switched Roger's son with his own grandson, to completely hide Roger's child identity and protect him as Roger asked him to. That would make Luffy Roger's son & Ace Garp's grandson.
I got to think how many people keep telling Luffy has "a mysterious air" and talks like Roger (Shanks, Crocus, Rayleigh & others) also Ace's habbit to sleep all of the time at the middle of conversations like Garp does & Whitebeard telling Ace his character is nothing like Roger's when Ace revealed his true identity to him…..
Of course I could be wrong
What do u think??