Board Thread:Lore Discussion/@comment-85.74.137.231-20130605091958/@comment-6948756-20131021164355

Regarding the original question (since some of the comments may have veered off topic slightly), the Song of the Dragonborn's second stanza is read as thus (emphasis added)

Hearken now, sons of snow, to an age, long ago

And the tale, bodly told, of the one!

Who was kin to both dov, and the races of man

With a power to rival the sun!

Considering this, it would mean that beastmen nor mer could be Dragonborn. And while Bretons are usually considered men, they are esentially TES's equivalent to half-elves in (for example) D&D. They did come around from generations of Altmer and Nords breeding, after all. Also, would Redguards count, since they're ancestrallyYokudan instead of Atmoran? Assuming all of the above is true, then only Nords and (IIRC) Imperials count.

It doesn't make much since from a gameplay perspective, though. Some fans like the other races, and thus they continue to be options. I personally have inumerable Altmer and Orsimer Dovahkiin.