Sir William was a Knight of the Garter, and inherited the barony of Clifford, of Lanesborough, from his mother. He succeeded his father as Duke in 1764. On 6 June 1774, he married Georgiana [d. 1806], daughter of John, 1st Earl Spencer. They had a son, William Spencer (who became the 6th Duke of Devonshire), and two daughters. Around 1790, the Duke commissioned the artist Gainsborough Dupont to paint his wife's portrait (now in the NGA). Three years after Georgiana's death, William married Lady Elizabeth [d. 1824], widow of John Thomas Foster and daughter of the 4th Earl of Bristol.
Bibliography
1965
Cooper, Douglas, ed. Great Family Collections. New York, 1965:147-168