Did you want to know or wait till the story progresses and you find out? You will probably figure it out unless it's already been told.
I have a hunch. But go on, please tell me
Spoil me please
Spoiler
From what I understand the white haired person that was talking to them in last episode, is or was a dragon, thats why even though the king hates magic he cant get rid of him. Now if he's a dragon/former dragon his sister has to be th dragon shown with the human in the last chapter. That dragon was the dragon of lengres- langres... the place where Seth is from, the reason why Seth is part dragon. Or the dragon could be Seth's mother.
That's what I have come up with and what I understand. Hope that helps :D
Was it mentioned who the white haired man’s sister is?