Board Thread:Lore Discussion/@comment-85.74.137.231-20130605091958/@comment-71.61.178.23-20130610000121

I think so....I may have been wrong, upon further research. So far, that's the only explanation I can think of that fits all the facts, though. So I think we can safely say that the Dragonborn Emporors were not Dragonborns in abilities, only those who carried the Dragon Blood. For now, and only until proven otherwise.