Joni Mitchell is one of the most influential singer-songwriters in modern musical history. But behind all of her fame and success, Mitchell was hiding a private loss: the separation from her daughter, Kilauren Gibb.

The singer became pregnant at 20 when she was a college student and had no support from the baby's father or her parents. Eight months after giving birth to a baby named Kelly Dale Anderson, Mitchell decided to place her infant daughter for adoption.

"The main thing at the time was to conceal it," Mitchell told the Los Angeles Times of her pregnancy in 1997. At the time, she was living in Toronto. "The scandal was so intense. A daughter could do nothing more disgraceful. It ruined you in a social sense. You have no idea what the stigma was. It was like you murdered somebody."

With no other options, she quickly married folk singer Chuck Mitchell, who agreed to help support Mitchell and her daughter - but the marriage unraveled almost immediately. It was then that she made an adoption plan for Kelly - who was renamed Kilauren Gibb by her adoptive parents.

"It left a hole in me that I didn't fill until the day I saw her again," Mitchell told PEOPLE of the adoption in 2000.

Mitchell kept that secret to herself until 1993, when a college roommate sold the story to a British tabloid, according to The New York Times. The singer felt betrayed - but the story brought visibility to Mitchell's search for her long-lost daughter. Gibb, who had also been searching for her birth parents, eventually put together that the details of their lives, as much as she knew them, matched up.

In 1997, Mitchell and Gibb were reunited after more than 30 years of separation and have had a relationship ever since. "It's kind of crazy," Gibb told The Toronto Star in 1997. "We met, and it clicked. It was like we never separated."

Mitchell gave birth to Gibb - then named Kelly Dale Anderson - in a Toronto hospital on Feb. 19, 1965. According to the Los Angeles Times, she stayed in the hospital for 10 days due to birth complications.

In a desperate attempt to keep her baby, Mitchell agreed to "a marriage of convenience, at best" with folk singer Chuck Mitchell, as she told the Los Angeles Times. "One month into the marriage, he chickened out, I chickened out. The marriage had no basis, except to provide a home for the baby." They divorced, and Mitchell placed her daughter for adoption.

"I gambled," Mitchell recalled. "I took what was behind the curtains. I gambled that the people who came forward to take this child wanted this child and felt like there was a hole in their life without this child."

Gibb was adopted at 8 months old

When Gibb was 8 months old, she was adopted by David and Ida Gibb, teachers from Toronto, who already had a son, David. They changed her name from Kelly Dale to Kilauren Gibb and didn't tell her that she was adopted until many years later.

On her fourth album, Blue, Mitchell included a song called "Little Green," about the daughter she named Kelly - as in Kelly Green. In the lyrics, she described a "child with a child" who had to make an impossible decision.

"So you sign all the papers in the family name," Mitchell sang. "You're sad and you're sorry, but you're not ashamed."

In 2000, Mitchell told PEOPLE she wrote the track "as a message in a bottle [to Gibb]." Once she reunited with Gibb, the singer recalled her daughter telling her, "God, it's so cryptic, Joan. I never would have known it was for me."

Gibb started looking for her birth parents as a teenager

When she was young, Gibb recalled to The Toronto Star in 1997, she started putting the pieces together that something was missing from her early childhood. "I would look at our family's album, and realize that there were no pictures of me before the age of 8 months," she said. "My mother tried to explain it away - I was a second child, and you don't take as many pictures of them. Or the camera wasn't handy at the time. But I always wondered."

Gibb added that she always felt loved by her parents, and that they felt they were doing the right thing by withholding information about her adoption. "They were nurturing, loving parents who wanted to protect me," she explained. "They didn't tell me because they didn't want me to feel like an outsider. And, they were afraid they might lose me."

Mitchell and Gibb reunited with the help of a fan

In 1996, Mitchell told The New York Times that she wanted to find her daughter, especially since the story was officially out in the open. "The good news is that I'm clean now, and I have no skeletons," she said. "But I worry, because there are a lot of things she should know, her genetic background, what diseases she's prone to. It would be nice if she could meet her grandparents while they're still alive."

In response, fan Wally Breese created a website to help filter people with a genuine chance of being Mitchell's daughter from the hordes of people claiming to be her. Improbably, it worked.

A friend was looking at the site and suggested Gibb get in touch because of the similarities in their appearances and because some of the details lined up between Mitchell's story and what Gibb knew about birth parents.

"The more I read, the more I realized how alike we were," Gibb told The Toronto Star in 1997. "She was a singer, I was into music. She was an artist. I painted. We both enjoyed the same things." Enough information matched that Breese referred Gibb to Mitchell's manager, and they connected from there.

"My purpose has always been to pay Joni back for all the music she's given the world," Breese told Wired in 1997. "But this is more than I could have hoped for."

After such a long search, Mitchell and Gibb first spoke on the phone, and then Gibb flew to her mother's Los Angeles home with her then-3-year-old son Marlin to meet her as an adult. (Gibb later had a daughter, Daisy.)

"It was wonderful," she told The Toronto Star. "It was a great relief to me in every way. It made me feel whole. It made me feel complete."

When they first met, Mitchell apologized for what had happened. "She wanted to get it off her chest, how sorry she was that she gave me up," Gibb recalled. "How broke she was at the time - she couldn't even get the money together to be in the musician's union. She couldn't tell her parents about the whole thing, having a baby - she was brought up in a Victorian household."

But Gibb was very happy to grow up with her family. "She asked me how my childhood was, and I was honestly able to tell her that it was fabulous," she described. "It was a great childhood, probably the best. I think now, that I could have been raised in California, and been a Bel Air brat. I'm really happy that I got my family to raise me, in down-to-earth style. I'll always be grateful for that."

Gibb met her biological father after meeting Mitchell

Following her reunion with Mitchell, Gibb met her biological father, Toronto photographer Brad MacMath. Mitchell told PEOPLE in 2000, "He has a daughter by one marriage and a son by another. We all go out together as a dysfunctional family."

MacMath later told TIME that it was a reunion he had long been hoping for. "I was always sort of looking for her on the street, even though I didn't know it," he said. "To have a grown daughter and grandson appear out of nowhere is absolutely amazing."

Mitchell and Gibb have a lot in common

In addition to their early careers as models and their passions for music and art, the two share a lot more in common. In 1998, Mitchell and Gibb talked to The New York Times about how they had similar tastes in clothes and handbags, and shared what Mitchell explained was a "crazy bravado that comes from the Irish blood."