Prince William, Duke of Gloucester and Prince George of Denmark, were eventually monarchs of Great Britain Kingdom in the 15th century.
Prince William, Duke of Gloucester (24 July 1689 30 July 1700 ) was the son of Princess Anne, later Queen of England, Ireland and Scotland from 1702, and her husband, Prince George, Duke of Cumberland. 
Prince George of Denmark and Norway, Duke of Cumberland (Danish: "Jrgen" ; 2 April 165328 October 1708), was the husband of Queen Anne, who reigned over Great Britain from 1702. 
