Sophia Sidney, Baroness De L'Isle And Dudley

Sophia Sidney, Baroness De L'Isle and Dudley (née FitzClarence), was born on 25 August 1796 in Somerset Street, London. She was the eldest illegitimate daughter of William IV of the United Kingdom and his longtime mistress, Dorothea Jordan, a comic actress. Her father, Prince William, Duke of Clarence and St Andrews, and Dorothea Jordan maintained a relationship for approximately twenty years, during which they were never married but lived together in domestic stability. In 1797, the couple moved from Clarence Lodge to Bushy House in Teddington, where they resided until 1807. The couple separated in 1811 as William sought to produce legitimate heirs.

Sophia had nine siblings, comprising five brothers and four sisters, all sharing the surname FitzClarence. Despite the lack of a formal marriage, her father’s relationship with Jordan was notable for its duration and the number of children produced.

On 13 August 1825, Sophia married Philip Sidney, later known as the 1st Baron De L'Isle and Dudley of Penshurst in Kent. Sidney was related to the Romantic poet Percy Bysshe Shelley; however, he chose to drop "Shelley" from his surname. The marriage produced four surviving children:

- Adelaide Augusta Wilhelmina Sidney was born on 1 June 1826 and died on 20 September 1904. She married her first cousin, Frederick Charles George FitzClarence-Hunloke, son of George FitzClarence, 1st Earl of Munster, but they had no children.

- Philip Sidney, 2nd Baron De L'Isle and Dudley, was born on 28 January 1828 and died on 17 February 1898. He was the grandfather of the 1st Viscount De L'Isle.

- Ernestine Wellington Sidney was born on 9 January 1834 and died on 20 September 1910. She married Philip Perceval and was the mother of Major Sir Philip Hunloke, father of Lt.-Col. Henry Hunloke.

- Sophia Philippa Sidney was born on 11 March 1837 and died on 12 May 1907. She married Alexander, Graf von Kielmannsegg, a descendant of Johann Ludwig, Reichsgraf von Wallmoden-Gimborn, who was allegedly an illegitimate son of George II of Great Britain.

In May 1831, Sophia was elevated to the status of a daughter of a marquess. In January 1837, she was appointed State Housekeeper at Kensington Palace. She held this position until her death three months later. She died in childbirth shortly after drawing a sketch of her gravely ill father. She was considered his favorite child, and her death was a significant source of grief for William IV, especially since he was estranged from her brother, the Earl of Munster. Sophia was remembered for her wit, charm, and gaiety. A memorial dedicated to her exists at St John the Baptist Church in Penshurst, and she is interred in the Sidney family vault at the same location.

The widowed Philip Sidney died in 1851.