@Chichiechi At one moment he did, he said to look back 8 years in his father's activity. The thing is if they said if it is his sister, he would ruin his father's legacy, which would show more weakness than saying it was his child. All he knows is that she is a descendent of the Kalistos bloodline, but by saying that she is his daughter is the easiest way to keep her with him and it is more plausible than saying that this is his father's "bastard" child (which we don't know is true yet until we get further into the story)