Actress Jill St. John has said that Kendall was her idol.
Cousin of Jack Cardiff
Kay is the sister of actor Cavan Kendall.
Kay met and fell in love with Rex Harrison, who was married at the time, after they appeared together in Marriage a la Mode (1955). Rex learned of Kay's leukemia from her doctor a couple of years later. He divorced actress Lilli Palmer and quickly married Kay in 1957, agreeing with the doctor never to tell her the reason for her failing health. They lived the good life up until the end.
Sister of Kim Campbell