Ok so I don’t have the link for the novel since it’s been a while since I read it, but the novel is completed but not all chapters got translated so I was letting it marinate lol. So Arelyn is NOT the daughter of the duke, she is the dukes niece! The last thing I remember was her mother (the dukes sister) died I implied through the novel that the imperial family knows about it but kept it hidden and I believe that the empress was friends with Arelyn biologically mother. If someone has read the novel please do correct me if I was wrong about the mother’s death! But Arelyn is the niece of the duke!

Why do I feel like she's not his daughter but maybe the woman that the empress knows since she looks so much like her. Could be a cousin or sister of his. Just my theory lol...