Robert Lyle Knepper was born on July 8, 1959 in Fremont, Ohio.
He is the son of Pat Deck and Donald Knepper and has a younger sister, Kay.
Donald is a veterinarian, and Pat worked in the props department at a community theatre in Maumee, where Robert grew up.
Robert joined a small acting group as a child, and was very active in high school theatre productions.
He graduated from Maumee High School in 1977 and went on to study drama at Northwestern University in Evanston, Illinois.
Immediately after college he started his career in professional theatre productions, and a few years later he also made his on screen debut.
In 2001 Robert married casting director Tory Herald and the following year they had their son Ben (Benjamin Peter). Robert lives with his family in Los Angeles.