Mackenzie Phillips Had A 10-Year Intimate Relationship With Her Dad

Actress Mackenzie Phillips poses for a portrait session at home holding a bumper sticker that reads "One Day At A Time" on December 3, 1976 in LA, California. Source: (Photo by Michael Ochs Archives/Getty Images)

To everyone watching Mackenzie Phillips throughout the ‘70s and ’80s it seemed like she had it all. She appeared in American Graffiti and starred in the hit sitcom One Day At A Time, not to mention the fact that she was singing in The New Mamas and The Papas with her father John Phillips. Regardless of how well her career was going, she was harboring dark secrets in her personal life. Not only was she heavily addicted to drugs, but she claims that she was in a decade long incestuous relationship with her father.