Del Kierson von Wincott (フォンウィンコット卿デル・キアスン) is the current ruler of the Wincott domains. He's the son of Odile von Wincott and the younger brother of Suzanna Julia von Wincott. He's also the father of Lindsey von Wincott.
In the anime, he and his sister Julia have very similar appearances. However, in the novel he's described as having green hair with brown bangs.