 On 2 March 1642, Legge married Elizabeth Washington (c. 1616–1688), "sister of another future royalist officer, Colonel Henry Washington".Her father, Sir William Washington, was the elder brother of Lawrence Washington, great-great grandfather of George Washington, while her mother, Anne Villiers, was the half-sister of James I's favourite, George Villiers, 1st Duke of Buckingham.With his wife Elizabeth, William Legge left three sons and two daughters.