He was the eldest son of Aubrey Beauclerk, 5th Duke of St Albans by his wife Lady Catherine Ponsonby.

His maternal grandparents were William Ponsonby, 2nd Earl of Bessborough (who served in both the Irish and the British House of Commons, and held office as a Lord Commissioner of the Admiralty, Lord Commissioner of the Treasury, Postmaster General of the United Kingdom, a Privy Counsellor, and Chief Secretary for Ireland) and Lady Caroline Cavendish (eldest daughter of William Cavendish, 3rd Duke of Devonshire).

After unsuccessfully approaching Francis Ferrand Foljambe, Fitzwilliam brought Beauclerk forward shortly before the 1790 general election and Etherington was persuaded to give his support.

Jane was daughter of John Moses, of Hull in York, and his first wife Margaret Etherington, who died at or shortly after her birth.

His widow and son both died on 19 February 1816 (at the home of her sister, the former Lady Laura Manners, wife of John Dalrymple, 7th Earl of Stair, in Portman Square, London)[8] and the titles were inherited by the 6th Duke's younger brother William, who became the 8th Duke of St Albans, who had thirteen children.