Key milestones in the life of Queen Elizabeth II, who died ON Thursday at Balmoral Castle in Scotland at age 96 after serving more than seven decades on the throne.April 21, 1926: Born Princess Elizabeth Alexandra Mary in Mayfair, London, the first child of the future King George VI and Queen Elizabeth, later called the Queen Mother. December 10, 1936: Elizabeth becomes heir-apparent to the throne after her uncle King Edward VIII abdicates and her father becomes king. October 13, 1940: Elizabeth makes first public speech at age 14 on the BBC Children's Hour to reassure children who had been separated from their parents during the Blitz. 1945: Elizabeth is made a Subaltern in the Auxiliary Territorial Service, serving for Britain during World War II. November 20, 1947: E