Board Thread:Lore Discussion/@comment-32666991-20171108134807/@comment-6326997-20190129044638

I think since the Dragonblood is a trait gifted to Mortals by Gods, then the birth of an heir to the Dragonborn is strictly decided by the Gods themselves. The player character has no in-game evidence that his family had Dragonblood. As a result there is nothing to directly infer that his or her children would inherit the gift from them. Instead, the game itself states many times that the Dragonblood is a gift.

All Septims were not Dragonborn. Potema, for example has never been shown to be a Dragonborn although her son clearly was as he served as Emperor. Instead, the Dragonblood was gifted from generation to generation. How is not really elaborated. It could be a form of mantling, or perhaps a less potent form of CHIM.

From the prophecy that has come true according to the Game and its contents, I don't see any reason to doubt that the word "last" means "final" not "latest". I could be wrong, Bethesda could also choose to rework the story, but I doubt seriously that they would. Each hero of each game is independent of one another, and so the Player Character of Skyrim being the last isn't really that big of a deal.