Kerwin’s first marriage was to actress
Hanna Hertelendy from 1953 to 1958. Kerwin had one daughter from his marriage to Hertelendy, costume designer Barbara Kerwin. In 1964, Kerwin married
Connie Mason, who he met while filming
Blood Feast. The couple had two daughters, Denise and Kim, and remained married until Kerwin's death in 1989. Kerwin was the brother of director Harry Kerwin and appeared in several of his films throughout the 1970s including ''God's Bloody Acre
, Barracuda and Tomcats''. All three of Kerwin’s daughters pursued film careers for at least a decade. Half-sisters Barbara and Kim Kerwin had bit roles in Herschell Gordon Lewis’
The Gruesome Twosome as children; William Kerwin himself did not appear in this movie. Both girls also collaborated with their uncle Harry Kerwin; Barbara had a small role in
Sweet Bird of Aquarius while Kim acted in
Cheering Section. Denise, William Kerwin’s youngest daughter, is the only of the three to never work with Lewis or Harry Kerwin during her acting career. A heavy drinker and smoker both on and off-camera throughout his life, Kerwin died from a heart attack on October 27, 1989 at his home in Hollywood, Florida at age 62. == Filmography ==