David Janssen was Nebraska-born, the son of a banker-turned insurance man father, and a mother Berniece who came from a farming family. Born David Harold Meyer, he took his last name from a stepfather Eugene Janssen, who Berniece married in Los Angeles in 1940. David's parents had divorced when he was 5 and mother and son moved West soon thereafter. Two half-sisters were born from Berniece's marriage to Eugene Janssen: Teri Jean in 1942 and Jill Eilleen in 1945. David also had stepsiblings from his father's marriage to Reva Kroeger in 1941: twin boys Larry and Lee Meyer were born in 1942 and a girl Gloria in 1946.
David Janssen was married twice: to Ellie Graham Goldfarb from 1958 to 1970 (they separated in 1968) and to Dani Goldman Crayne from 1975 to Janssen's death in 1980. He had no children of his own, but stepchildren from both marriages. He also shared a home with actress Rosemary Forsyth for a period of time after his separation from Ellie (1968-1971).
The following chart shows 5 generations of David's direct line of ancestry. His maternal grandparents were Swiss-German and Irish. His paternal grandparents were of German and Scottish/Welsh ancestry. More family history information will be published if there is sufficient interest.