The black haired dude, who is obviously Claude's older brother, as mentioned before he and Jennette's mom had an affair.
So my theory is that, Jennette isn't Claude's daughter instead, her father was the black haired dude, who is Claude's older brother, explaining her blue crystal eyes.
Sir Whitey, in the original story, just revealed that Jennette is Claude's daughter just for the throne and planned to use her as a mean of revenge of black haired dude as he is an accomplice.
Just a theory. (づ ̄ ³ ̄)づ
Spoiler:
I think it was shown in the story how jennette came to be. I remember before his brother died he used black magic to create jennette inside her mom's stomach (yeah i know, weird) He's using jennette to get to claude thats why in the original story, claude ended up suffering right after he killed atty. I dont know how the brother is alive tho cause they showed him dying.










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