Tatum penned a detailed memoir, "A Paper Life," in 2004 that became a New York Times bestseller, followed by, "Found: A Daughter's Journey Home," her new book released this week as the OWN show debuts, that recounts her attempt to repair her fractured relationship with her dad.
Their estrangement was so severe that Ryan did not even recognize his daughter when she attended the funeral of Fawcett, who passed away in 2009 after a long battle with cancer.
Tatum claimed that her dad hit on her at his lover's funeral, telling radio host Howard Stern, in an interview this week while promoting the show, that Ryan, "just saw this blonde hair and was like 'Hey baby!' and I was like, "Dad -- it's me!'"
Tatum noted to Stern that Ryan later bragged about the incident to Vanity Fair, adding, "He doesn't even know the difference of what makes him look bad."
'We Have a History'
Yet it was Fawcett's death that opened Tatum to the possibility of reaching out to Ryan again.
"That was the last thing to help to soften my resolve and help make a relationship work and help build the bond back," Tatum told "GMA." "And that was before the show was even a possibility."
Father and daughter knew, they both told "GMA," they had to take advantage of the only thing they shared, show business, to try to heal old wounds.
"This [the OWN show] looked promising because we work well together," Ryan said. "We have a history and I thought maybe we could make more history."
Ryan and Tatum's early history seemed, from the outside, like a Hollywood fairy-tale.
The two co-starred together in the 1973 movie "Paper Moon," for which Tatum won the Best Supporting Actress Oscar at age 10, the youngest actress to ever do so.
While her father appeared handsome and charming on-screen, Tatum O'Neal has described growing up with him as "very toxic" and by the time she entered her teen years, said her bond with her father was unraveling.
"I don't think he had any idea what to do with me, at all," she told "Nightline" anchor Cynthia McFadden in an interview promoting "Found". "I think he was fine when I was a little kid and he could take me around and we went everywhere together."
"I think as I grew breasts and kind of became a young woman, I think he just got weirded out and kind of started to struggle with me, it seemed, a lot," O'Neal continued. "I started to get unbalanced and I started to feel insecure, and I started to not know where to turn."
It was also this time when Ryan, now divorced from Tatum's mother, began to date a series of high-profile Hollywood women, including actresses Anjelica Huston, Bianca Jagger and then Fawcett, who he was with until 1997.
"He is getting older, has battled leukemia," Tatum reveals on the show of why it was Fawcett who, in the end, brought them together. "And how would I feel if my father were to get sick or die? Would I be OK? And I realized I wouldn't be OK. So I knew I needed to make an effort."
Both Ryan and Tatum told "GMA" the effort has been a struggle that, even today after the series has stopped filming, they continue to confront.
"I'm sensitive and I wish I was less sensitive," said Tatum. "But it's a nice feeling to feel that I have a parent and that we've done this show."
"It's challenging but it's worth it to have her back in the fold," Ryan said of his daughter. "She's still my little girl."
ABC News' Lauren Effron and Steven Baker contributed to this story.