Philip's mother, Princess Alice of Battenberg, was born at Windsor Castle to her parents in 1885 Alice, who was one of the great-grandchildren of Prince Louis of Battenberg and Queen Victoria of Hesse, was born with congenital deafness and learned to read lips, Tatler reported.

In 1902, Princess Alice met her husband, Prince Andrew of Greece and Denmark, at the coronation of Edward 7. The two married in 1903 "at the Old Palace" in Darmstadt, Germany, "in front of a glittering gathering of 200 sovereigns, princes, diplomats and cabinet ministers," according to the New York Times. They then moved to Greece and received 5 children, of which Prince Philip was the youngest and their only son.

However, when he was expelled from Greece in 1922, the family faced many difficulties. Mental health problems led to Princess Alice being "sent to the Tegel clinic in Berlin" without her consent, according to the British Psychological Society. Despite describing her as "sane," Sigmund Freud and his associates "believed that Princess Alice's religious delusions were the product of sexual frustration and advised her to X・ray her ovaries to kill her libido," the outlet reported. After treatment at this institution, "She did not see Prince Philip for years and wandered around Europe," the British Psychological Society noted.

After leaving Berlin, Alice returned to Athens, Greece, where, through a Greek reporter, she found a school for a nun named Martha and Mary's Christian Brotherhood.

For the last two years of her life, Princess Alice lived at Buckingham Palace with her son, Prince Philip, and his family, Per Tatler. She died in 1969, aged 12-5, at the age of 84. But before she died, Princess Alice wrote to Philip.

Even though they spent much of their lives away from each other, Princess Alice expressed great feelings for her son in her last letter to him.

"Dear Philip, be brave and remember that I will never leave you, and when you need me most, you will always find me," she wrote (via the Daily Mail). "All my devoted love, your old mom.""