August 13, 1090 – Death of Constance of Normandy, daughter of King William I of England (the Conqueror), buried at St. Melans near Rhedon in France
Born around 1066, Constance was one of the daughters of William I and Matilda of Flanders. She married Alan IV, Duke of Brittany in 1086. Constance was supposedly poisoned by her servants.
Wikipedia: Constance of Normandy
August 13, 1792 – Birth of Queen Adelaide of the United Kingdom, wife of King William IV of the United Kingdom, born Adelaide of Saxe-Meiningen at the Elisabethenburg Palace in Meiningen, Duchy of Saxe-Meiningen, now in Thuringia, Germany
Full name: Adelheid Louise Theresa Caroline Amelia
Unofficial Royalty: Adelaide of Saxe-Meiningen, Queen of the United Kingdom