Came of an old Northamptonshire family. His father Robert (d. 1656) was a Cromwellian who made a fortune in Dublin, and he himself supported William of Orange and in 1695 became a prominent member of the Irish privy council. In 1716 he was created a viscount. He was succeeded by his two sons, John, 2nd viscount (1679–1726), and Richard 3rd viscount (1680–1758), the latter of whom saved Marlborough’s life at the battle of Ramillies and rose to be a field-marshal. The 3rd viscount’s son Richard Nassau (1748–1793) succeeded to the title, which has descended accordingly.
