On top of the Aesir blood and favor, Volsung married the daughter of a giant, Hjlod -- a giantess and "wish-bringer" in Odin's service. (Hjlod was also the person who provided Rerir with the apple which produced Volsung.) It was from his giantess of a wife that the twins Signy (from last week's blogpost) and Sigmund were born (Sigmund was, by the way, the toughest, most powerful, most impressive man around), and from Signy and Sigmund's incestual affair, Sinfjotli was born.
|Sigmund the Fabulous|
And we still haven't made it to Sigurd, the supposed hero of our Saga.
|Sigurd slaying Fafnir|
Which brings us, finally and at last, to Sigurd, born of Hjordis after his father's death, and his own tragic tale of love and betrayal. Just in case you hadn't already had enough of it.
Odin > Sigi > Rerir > Volsung > Sigmund > Sigurd, with a mixed heritage of no less than three races. Which is probably why he got to slay the dragon.