User blog comment:B214/Light Novel Volume 16 spoilers/@comment-5185939-20131020211301/@comment-1359322-20131021034101

Magicians are humans, Le Fay is a human, Georg is a human too. It's more to their bloodline thing. Like Georg's family are all Magicians. So in this case it could be that one of Rugal's parents is a Magician.