Mackenzie Phillips

Mackenzie Phillips will return to the The Oprah Winfrey Show Friday with her half-sister, Chynna Phillips, to talk more about her claim that she had a sexual relationship with her father, US Weekly reports.

Chynna will be in the studio while Mackenzie will appear via satellite, US said.

Mackenzie's family reacts to her startling claims

The One Day at a Time actress made headlines this week with the release of her new memoir, High on Arrival. In the book, and on Wednesday's Oprah, Mackenzie said that her father, John Phillips, first had sex with her when she was 19 years old. Mackenzie also said she and John, the lead singer of the Mamas and the Papas, went on to have a consensual sexual relationship for almost ten years. She said the affair ended when she became pregnant and, unsure of the father, had an abortion.

Family reaction to Mackenzie's accusations has been mixed. Chynna told US she "knew it was true," but John's second and third wives, Michelle Phillips and Genevieve Waite, both said they didn't believe Mackenzie.

VIDEO: Phillips tells Oprah that John shot her up with heroin for the first time

Mackenzie followed her highly publicized Oprah appearance with an interview on Today with Meredith Vieira Thursday. She said her father "was not a bad man, just a very sick man... He didn't set out to hurt me."

John Phillips died in 2001.

Mackenzie, 49, is the daughter of John and his first wife, Susan Adams. Mackenzie has a brother, Jeffrey, as well as three half-siblings: Chynna, John's daughter with Michelle; and model-actress Bijou Phillips and Tamerlane, whose mother is Waite.