About Eliza Courtney
Elizabeth Courtney (20 February 1792 – 2 May 1859) was the illegitimate daughter of the Whig politician and future Prime Minister Charles Grey, 2nd Earl Grey, and socialite Georgiana Cavendish (née Spencer), Duchess of Devonshire, while Georgiana was married to William Cavendish, 5th Duke of Devonshire. The Duchess was forced by her husband to relinquish Eliza shortly after her birth, to be raised by Charles Grey's parents, Charles Grey, 1st Earl Grey, and Elizabeth Grey. The Duchess came to visit Eliza in secret. Eliza named her firstborn daughter Georgiana. The name Courtney, extinct since the death of Charles Kelland Courtney in 1761, was derived from her great-uncle, her maternal grandmother's brother, William Poyntz (d. 1809), having married Isabella (d. 1805), sister and co-heiress of the aforementioned Charles Courtney, the last of the west country family of Courtney of Trethurfe and Courtney of Tremeer. Eliza's first daughter, Georgiana, was born on 12 October 1817. Her brother was Freeman Freeman-Thomas, Viceroy of India, and was created 1st Marquess of Willingdon.
Biography source: Wikipedia. The profile adds birthday-specific historical context from the Celebs Birthday Today editorial database.