Rockingham was the eldest son of Edward Watson, 2nd Baron Rockingham and his wife, the former Lady Anne Wentworth, daughter of Thomas Wentworth, 1st Earl of Strafford. In 1677, he married Lady Catherine Sondes, a daughter of George Sondes, 1st Earl of Feversham.
They had five surviving children:
Edward, styled Viscount Sondes (c 1687 – Kensington, 20 March 1721/1722), married on 21 March 1708 Lady Catherine Tufton (24 April 1693 - 13 February 1733), daughter of Thomas Tufton, 6th Earl of Thanet and Lady Catherine Cavendish, parents of the 2nd and 3rd Earls of Rockingham and Catherine Watson (d April 1765), who married on 21 August 1729 Edward Southwell (1 June 1705 - 16 March 1755), son of Edward Southwell and Elizabeth Cromwell, 8th Baroness Cromwell, and had Edward Southwell, 20th Baron de Clifford. Lady Margaret (1695–1751), married John Monson, 1st Baron Monson. Honorary George (d 1735)
Lady Mary (d 1737), married Wray Saunderson.
Lady Arabella, married Sir Robert Furnese, 2nd Baronet.
Lord Rockingham was Master of the Buckhounds from 1703-1705, Custos Rotulorum and Lord Lieutenant of Kent from 1705-1724, Vice-Admiral of Kent in 1705 and Deputy Warden of the Cinque Ports from 1705-1708.
From 1681-1685, Watson was Whig Member of Parliament for Canterbury and for Higham Ferrers briefly in 1689, before having to leave the Commons on inheriting his father"s barony that year.
