Chynna Phillips and Mackenzie's "One Day at a Time" co-star Valerie Bertinelli have since rallied around her.

CNN: John Phillips had checkered, sometimes sordid, life

"Somebody could have dropped a piano on my head, and I probably wouldn't have felt it, " Chynna Phillips told the magazine.

CNN: John Phillips had checkered, sometimes sordid, life

She told Chynna Phillips, her half-sister, about the affair in the late '90s, according to an interview with Chynna in Us magazine.

CNN: John Phillips had checkered, sometimes sordid, life