Mountbatten-Windsor is the family surname available to and used by descendants of Queen Elizabeth II and Prince Philip, Duke of Edinburgh, when a surname is required. Generally, those who are entitled to, and use, the royal style HRH Prince or Princess have no need for a surname. A surname may become needed, for example to register a marriage, and for non-royal children. Mountbatten-Windsor combines Elizabeth's house name of Windsor and Prince Philip's adopted surname of Mountbatten, the name his maternal family the House of Battenberg adopted in 1917. Its use was authorised in a declaration by the Privy Council in 1960. The male line ancestry of the Mountbatten-Windsors is through the House of Glücksburg, the senior surviving branch of the German House of Oldenburg, one of Europe's oldest royal houses.