Princess Cecilie of Greece and Denmark, Hereditary Grand Duchess of Hesse, was the older sister of Prince Philip, Duke of Edinburgh. HRH The Duke of Edinburgh His Royal Highness The Prince Philip, Duke of Edinburgh, KG, KT, OM, GBE, AC, QSO, PC, (Philip Mountbatten, formerly Prince Philip of Greece and Denmark) (born 10 June 1921) is the consort of Queen Elizabeth II of the United Kingdom. ...

She was born in Greece on 22 June 1911, the daughter of Princess Alice of Battenberg and Prince Andrew of Greece. Princess Alice of Battenberg Princess Alice of Battenberg, later Princess Andrew of Greece and Denmark (25 February 1885 - 5 December 1969) was a great-granddaughter of the British Queen Victoria who married into the royal house of Greece. ... Prince Andrew of Greece and Denmark (January 20, 1882 - December 3, 1944), of the House of Schleswig-Holstein-Sonderburg-Glücksburg, was the son of George I (1845-1913), King of the Hellenes, and of Grand Duchess Olga Konstantinova (1851-1926) of Russia. ...

She had three sisters and one brother:

• Princess Margarita (1905-1981)
• Princess Theodora (1906-1969)
• Princess Sophie (1914-2000)
• Prince Philip, Duke of Edinburgh (1921 -)

She married the Hereditary Grand Duke Georg Donatus of Hesse-Darmstadt on 2 February 1931. They had three children: Prince Ludwig Ernst Andreas (born 1932), Prince Alexander (born 1933), and Princess Johanna (born 1936). Georg Donatus' father, Grand Duke Ernst Ludwig of Hesse died in October 1937. A few weeks after the funeral, Ernst Ludwig's younger son, Prince Ludwig was due to be married to Margaret Geddes. On 16 November 1937, Princess Eleonore, Georg Donatus, Princess Cecilie, and their two young sons, left for England, where Prince Ludwig was due to be married. The aeroplane hit a factory chimney near Ostende and crashed into flames, killing all those on board. The only survivor of the family was Johanna, she was not on the plane at the time. Johanna was adopted by Prince Ludwig and Margaret, Princess of Hesse by Rhine, however, she died in 1939 from meningitis. HRH The Duke of Edinburgh His Royal Highness The Prince Philip, Duke of Edinburgh, KG, KT, OM, GBE, AC, QSO, PC, (Philip Mountbatten, formerly Prince Philip of Greece and Denmark) (born 10 June 1921) is the consort of Queen Elizabeth II of the United Kingdom. ... Ernst Ludwig Karl Albrecht Wilhelm Großherzog von Hessen und bei Rhine or Ernest Louis of Hesse (25 November 1868-9 October 1937) was Grand Duke of Hesse-Darmstadt from 1892 until his abdication in 1918. ...