@GruntZone360 As someone that binged this whole series a few weeks ago, so fresh in memory, I don't think it's ever been explicitly stated that he isn't, but it's clear she misunderstands his exact position, and heavily implied her assumption is wrong.
@Haruka That is impossible since there are hints he is related to the Emperor, maybe his child. And the Emperor's type is voluptuous beauty. He is not the Emperor's type.