MacKenzie Phillips’ siblings Bijou Phillips and Chynna Phillips have come forward regarding their sister’s sexual relationship with their father, John Phillips of the Mamas and Papas.

Both siblings stand by their sister and say they have known about the incest for a long time. But her stepmother, Michelle Phillips, also of the Mamas and Papas, says MacKenzie’s claims are untrue.

Michelle spoke with the Hollywood Reporter about the day MacKenzie told her she had consensual sexual relations with her father. She said, “She told me, then she called me back and said, ‘You know I’m joking.’ I said it wasn’t funny. Mackenzie said, ‘I guess we have different senses of humor.’”

She continued, discrediting MacKenzie and even taking a stab at Oprah.

“I think it’s unconscionable that Oprah would let her do her show. I have every reason to believe it’s untrue. Oprah should be more judicious about who she has on her show.”

Then she went on to say how Mackenzie’s past should speak for itself.

“Mackenzie has a lot of mental illness. She’s had a needle stuck up her arm for 35 years. She was arrested for heroin and coke just recently. She did ‘Celebrity Rehab’ and now she writes a book. The whole thing is timed. Mackenzie is jealous of her siblings, who have accomplished a lot and did not become drug addicts.”

Harsh words. But Michelle’s daughter Chynna has since explained why her mother responded the way she did. She says she is angry at the publicity.

“It’s not something that my mom wants plastered all over the papers. Am I exceedingly joyful that my family secret that I told maybe my therapist, my husband and my very best friend in the whole word [is now public]? No.”

But she is still standing by her sister. She does admit that the news was like a punch to the stomach when she first found out, 12 years ago. “I was completely stunned. I walked around in a comatose state for about 10 days.”

Bijou Phillips, MacKenzie’s youngest sister, is also standing by her sister but is devastated by the publicity it has gotten. She released the following statement:

“When I was 13, Mackenzie told me that she had a consensual sexual relationship with our father. This news was confusing and scary, as I lived alone with my father since I was 3, I didn’t know what to believe and it didn’t help that shortly there after Mackenzie told me it didn’t happen …. I understand Mackenzie’s need to come clean with a history she feels will help others, but it’s devastating to have the world watch as we try and mend broken fences, especially when the man in question isn’t here to defend himself.”