William IV (Guillaume Alexander; French: Guillaume Alexandre; 22 April 1852 – 25 February 1912) reigned as the Grand Duke of Luxembourg from 17 November 1905 until his death. He succeeded his father, Adolphe. William was a Protestant, the religion of the House of Nassau.
William (4 July 1535 – 20 August 1592), called William the Younger (German: Wilhelm der Jüngere), was Duke of Brunswick-Lüneburg and Prince of Lüneburg from 1559 until his death. Until 1569 he ruled together with his brother, Henry of Dannenberg. William was the son of Ernest I, Duke of Brunswick-Lüneburg.
Robert I, Duke of Normandy (c1000-1035) William I, King of England (1027-1087) ... Count of Nassau in Dillenburg; From William the Rich to Johan Willem Friso.