I dont think he is her father, but it was mentioned earlier in the story that she might be a child from his father so his half sister.
Nope... he's her daddy
the latest chapter 48- it was worded a little oddly but when he said she lived far towards the sea, he meant that she lived past the age of 17 where everyone thought she died and Halin would be impossible. but his next line is that she left the arms of goddess meaning her soul has passed.
Oh thank you for the explanation.
Duke you are her father. You might have forgotten your lover. But surely you are her father. So according to comic, her mother is alive or not?