Foster was born in 1780, possibly in
Ireland, to
John Thomas Foster (d. 1796) and
Lady Elizabeth Hervey, daughter of
Frederick Hervey, 4th Earl of Bristol. He went on to study at
Drogheda Grammar School and
Christ Church, Oxford. He enjoyed a comfortable social situation; his father was the Irish MP for
Ennis and first cousin of
John Foster, 1st Baron Oriel and
William Foster, and his mother, Lady Elizabeth Foster, would later go on to marry
William Cavendish, 5th Duke of Devonshire, was herself the daughter of
Frederick Hervey, 4th Earl of Bristol. Augustus had one older brother, Frederick (1777–1853) and an elder sister Elizabeth (b. 1778), who died several days after birth, as well as two illegitimate half-siblings fathered by Devonshire. Augustus's parents separated in 1781, at which time he and his brother remained in the care of his father while his mother moved to
Chatsworth House. He courted
Anne Isabella Milbanke (later 11th
Baroness Wentworth and wife of
Lord Byron), but on 18 March 1815, one year after his arrival in Denmark, he married Albina Jane Hobart (2 May 1788 – 28 May 1867), daughter of Hon.
George Vere Hobart (1761–1802), second son of
George Hobart, 3rd Earl of Buckinghamshire. In 1832, she was raised to the rank of an earl's daughter by
royal order — and was thus styled Lady Albina — after her brother,
George Hobart, 5th Earl of Buckinghamshire, succeeded
their uncle as
Earl of Buckinghamshire. He and Lady Albina would go on to have three sons: • Frederick George (3 January 1816 – 25 December 1857), succeeded as 2nd Baronet • Rev. Cavendish Hervey (7 May 1817 – 27 November 1890), succeeded as 3rd Baronet •
Vere Henry Louis (1819–1900), philanthropist and educationalist ==Career==