Board Thread:Oblivion/@comment-9716469-20130519212835/@comment-26474238-20130520164851

AzuraKnight wrote: Maybe it was somehow enchanted by Akatosh when he created it to only recognize a Septim or being a desendant leave a small diluted amount of dragon blood (though the lore would say no) and that lets the wear the amulet.

A actual Dragonborn has the blood and soul of a dragon its a rare blessing from Akatosh not something that is fully passed down to another generation. As the Dragonborn page says (copy/paste) -

"The first Dragonborn was purportedly Saint Alessia, the Nedic slave queen who was blessed by Akatosh and given the Amulet of Kings to seal the covenant between them. This began the tradition of all legitimate rulers of the Cyrodilic Empire referred to as Dragonborn as only they could wear the Amulet of Kings and light the Dragonfires..."

"Dragonborn scarcely exist, and it is rare for more than one to appear within an era. They can belong to any race or gender, since the Dragon blood is a "gift" bestowed to certain mortals favored by Akatosh."

Septims are all referred to as Dragonborn as a title not as a actual Dragonborn (like Alessia, Tiber Septim, the player or Miraak). Thats the way i interpret it anyway. Do not trust everything on wikis. They can be edited by everyone, you must remember. Play Oblivion again, though. It is specifically mentioned that the Amulet can only be worn by those with the dragon blood, which is why an heir of Uriel is needed to re-light the dragon fires. In your first dialogue with Uriel before he is killed, he'll even mention that his other heirs are dead, forcing you to find his illegitimate son, meaning that the gift of the dragon blood is indeed passed down from parents to their children.