Board Thread:Lore Discussion/@comment-85.74.137.231-20130605091958/@comment-3573184-20130812205914

As The book of the Dragonborn states

http://elderscrolls.wikia.com/wiki/The_Book_of_the_Dragonborn

" Very few realize that being Dragonborn is not a simple matter of heredity - being the blessing of Akatosh Himself, it is beyond our understanding exactly how and why it is bestowed."

Any issues of heridity are nonexistant.

Miraak, Alessia, Reman, Tiber, Wulfharth, Mankar Camron, and The Dovahkiin are all dragonborn, and all unrelated to eachother.