1.) a dynasty that is devoted to incest. and only, incest.
2.) a dynasty that is fully pure-blooded and has multiple deformities because of this incest.
person1: you guys hear about that seacake dynasty?
person2: yeah! i heard it's devoted to incest!
person3: no way?! i'm joining, my sister is hot!
person4: nope, you gotta be a full-blooded seacake to join, brah.