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they should not have relationship other than brother and sister as its scintifically wrong they wont get a baby as they are born from same father , and it causes biological mutations
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Ran is a daughter from the wife's first husband so they are no way related by blood. Though they are considered as siblings by paper. Since the former duke allowed Ran's name to be encoded in the family registry. If Yustaf is the ML (which I think he is lol) he have to remove or alter(?) her position from the family Registry.
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1. they not from the same father, her mother remarried!
2. ML didn't and never seen her as his sister!
3. she comes from another world and had different life
4. they not related by blood
5. you can't force ML to be her brother if he does not see her as his sister and he has any right to feel that way!
so no their relationship is not of sister/brother in any shape or form no matter how much you try to force this shit on the story.
i want RASHTA TO DIEEE with that idiot emperorrrrr , I reallyy like that preistt , i wanted NAVIER COULD SLAP THAT STUPID BITCH AND THAT emperor