Sullavan's third marriage was to agent and producer Leland Hayward, Sullavan's agent since 1931. At the time of the marriage on November 15, 1936, Sullavan was pregnant with the couple's first child. Their daughter, Brooke, was born in 1937 and later became an actress. The couple had two more children, Bridget (1939 – October 17, 1960) and William III "Bill" (1941–2008), who became a film producer and attorney. In 1947, Sullavan filed for divorce after discovering that Hayward was having an affair with socialite Slim Keith. Their divorce became final on April 20, 1948.