Board Thread:General Discussion/@comment-5647122-20140717042151/@comment-14027812-20140717060929

He's both, Dragonborn are individuals who are granted a dragon's soul by Akatosh. They're not necessarily born with it, and the Dragonborn status is often discussed through great legnths (there seems to be major differences between the type of Dragonborn that the Dovahkiin is, and the type that the Septims are). The soul is treated like a human soul and the person themselves are much like a normal being, but with the addition of also having the nature of dragons.