1/3
1 Year of Service
or the folk of the British Isle, wait, maybe a bad example, terrible teeth, penchant for world domination, cause of most global warfare in the last 300 years, maybe incest not so good in real life, but oh so satisfying in pixelsI would argue that even generations of inbreeding like in case of the Incas, Ancient Pesrian kings and Greek rulers of Egypt (aka Cleopatra) very rarely caused any problems.
Habsburgs are one of a few bad examples among many neutral ones.