Lord Augustus Fitzroy (1716-1741), was the third son of Charles, 2nd Duke of Grafton (1683-1757) and his wife, Lady Henrietta (1690-1726), the daughter of Charles Somerset, Marquess of Worcester. In 1733/1734, he married Elizabeth Cosby (1721-1788), daughter of Colonel William Cosby, Governor of New York, at Fort George, New York, and had two sons with her. Fitzroy served in the Royal navy and was present at the siege of Cartagena in February 1741. He died from fever in Jamaica three months later.
Another miniature of the sitter, at a younger age, also by Zincke, existed formerly in the collection of Euston Hall.