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yes, he is the brother. i think in the first world, he wanted to use jeanette and kill claude to get the throne but ati wasnt a part of this plan, she was just supposed to be a sacrifice. however now, ati has an importance to claude which wasnt a part of his plan so in the latest chapter he tried to kill her by tampering with her hair pin. tho other than the fact that he is the brother "the plan to get back the throne" part is just a theory of mine( ̄∇ ̄")

Please with caution!
So I’ve thinking about the guy with black hair she saw who had black eyes, but with that blue tint. Is it possible that he could be the older brother? And if so is it possible he may want the thrown back. Him and the king look offly similar. Which leads me to my theory...if it is the brother could he have changed place with the king in the story book.