In 1936, he married his second wife, Lady Isabel Violet Kathleen Manners (1918–2008), the second daughter of John Manners, 9th Duke of Rutland and Kathleen Tennant. His wife was prominent in society at Palm Beach. Together, they were the parents of son and a daughter:   In a reversal of the outcome of his first marriage, in 1951, Lady Isabel was granted a divorce after accusing him of adultery, which he did not contest. On 7 April 1951, he married his third wife, the socialite Gloria Rubio y Alatorre (1913–1980), who had been the wife of Prince Ahmed Fakhry Bey of Egypt, grandson of King Fuad I of Egypt. Her daughter, Dolores married his eldest son, Patrick Benjamin Guinness (1931–1965). On 31 December 1988, Guinness died of heart disease at The Methodist Hospital in Houston, Texas, United States. He was buried with the remains of his third wife at the Bois-de-Vaux Cemetery, Lausanne. Through his son Patrick and his stepdaughter Dolores, he was the grandfather of Maria Alexandra (born 1956), who married Foulques, Count de Quatrebarbes (born 1948) in 1979, Loel Patrick Guinness (born 1957), and Victoria Christina Guinness (born 1960), who married Philip Niarchos in 1984 (son of late Greek billionaire Stavros Niarchos). Through his son William, he was the grandfather of Sheridan William Guinness (born 1972), Thomas Seymour Guinness (born 1973), and Chloë Belinda Vane-Tempest-Stewart (born 1976), who married Lord "Reginald" Alexander Vane-Tempest-Stewart (born 1977).