So I was wondering how the will of D. is passed on. We have seen three cases where the will of D. was shown to be passed on and they were all from generation to generation by birth. Luffy got it from Dragon, Dragon got it from Garp and Ace got it from Roger (and Rouge?). In each case the will was passed on along with the last name. Now this made me wonder. Is it merely in a name? Or is there more to it?
Ace would probably be the best example. He chose to go through life using his mother's name Portgas D. Now what if Ace's mother would not have been a carrier, would Ace have not have had the will of D because of his name? Or what if Ace's mother married some other guy who didn't have the will of D, would she be unable to pass it on, because children are given their fathers name? This sounds pretty sexist to me, so it made me wonder whether just having the right surname is enough for someone to have the will of D or if there is some other way to become a D or to pass on the will of D?
If there isn't, the will of D will probably die out pretty soon...