Duke Preminger is Nadja's grandfather, and head of the Preminger household. He is a cold man who is very concerned with the importance and continuation of the Preminger good name. Social status is important as well, so he was very upset when Colette disobeyed him to be with Raymond. He has a poor relationship with his son, Herman, and does not wish his title to pass down to him. Instead he would see it go to his granddaughter Nadja. Therefore he hires some private investigators, Rosso and Bianco, to locate Nadja for him.

(Taken from "www.niko-niko.net")