Prince Constantijn of the Netherlands (Constantijn Christof Frederik Aschwin; born 11 October 1969) is the third and youngest son of the former Dutch queen, Beatrix, and her husband, Claus von Amsberg, and is the younger brother of the reigning Dutch king, Willem-Alexander. He is a member of the Dutch Royal House and currently fourth in the line of succession to the Dutch throne behind his nieces.