Comment by Kekekek on The Flower Dance and the Wind Song - Chapter 47

Eh not sure but I thought he was indicating the duke's luck on ella's love tho

I'm guessing because of what he has against Harsen. Caron is shown to be very protective of his sister, so if she didn't like her husband it would be easier if he was trying to bring him down, because she wouldn't stick by him. But since she likes Harsen, she might try to get in the way, or at least would be upset, if Caron ever turns against him.