Her Wikipedia article has this about her family, "Alexandra was the second eldest daughter of Ernest Augustus, Crown Prince of Hanover (1845–1923) and Princess Thyra of Denmark (1853–1933), the youngest daughter of Christian IX of Denmark (1818–1906) and Louise of Hesse-Kassel (1817–1898). Alexandra was a great-great-granddaughter of George III of the United Kingdom (1738–1820) and Charlotte of Mecklenburg-Strelitz (1744–1818)."