I think they are step siblings, with the possibility that his mother cheated on the kimg I guess
Srry didn't mean to down vote ಢ‸ಢ
No they are not siblings or step siblings at all this empress used magic to make Blaine's hair white which is a symbol of royalty in Estia and she also used magic on the emperor to convince everyone that Blaine is his child, but in reality Blaine is not, his hair is also brown like his mother, well it will be revealed at the end.
Oh my god !!!
oh wow- thank u!
are Blain and Lia biological siblings?