William Wyndham was the eldest son of John Wyndham (d. 1649) and grandson of Sir John Wyndham of Orchard Wyndham (a descendant of Lady Margaret Howard, a younger daughter of the 1st Duke of Norfolk), by his wife Catherine Hopton, daughter of Robert Hopton of Witham, Somerset.
Wyndham married Frances Hungerford, daughter of Anthony Hungerford of Farleigh Castle, Somerset on 8 June 1653 and had five sons and six daughters[1] including: