Liv Tyler was 11 years old in August 1988 when she looked up at a poster of Aerosmith frontman Steven Tyler on her bedroom wall and came to a realization that would rock her entire existence. "My mom has a diary entry or something where I wrote, 'I think Steven is my father,'" she explained in 1997. Soon afterward, she confronted her mother, model and musician Bebe Buell, and discovered that her suspicion was correct.

Up until that point, Liv believed that Utopia singer Todd Rundgren was her biological father. Buell, who was the Miss November 1974 Playboy Playmate, had a brief fling with Steven in late 1976, which ultimately resulted in their daughter's birth in New York City the following July. Rundgren knew there was a chance he wasn't Liv's father, but he signed her birth certificate, gave her his last name and stepped in to raise her as his own anyway.

Buell had decided to keep the paternity a secret from Liv because of Steven's reported drug addiction at the time. She has said that she and Rundgren "made a pact that he would be Liv's father and if it ever became an issue, we'd tell her at 18."

Before knowing he was her father, Liv felt a strong connection with Steven

Liv eventually figured out her biological father's identity long before then, however. She first met Steven when she was around 8 or 9 years old at one of Rundgren's concerts and recalls him buying her a Shirley Temple at the bar. Despite having "no idea who he was," the actress says she "fell madly in love with him" and even bought and would talk to his posters.

"It must be chemical somehow – DNA and genes," Liv explained. "I felt a connection in a very strong way when I met him as a little girl and I didn’t know why at first, but I figured it out rather quickly."

Credit that, in part, to her striking resemblance both to him and his daughter Mia Tyler (with his second wife Cyrinda Foxe), who was born just more than a year after her. "I saw her standing at the side of the stage at a concert and I was literally like looking at my twin," Liv said, noting they also have similar mannerisms.

After discovering the truth, she and Steven began fostering a father-daughter relationship, and she eventually changed her last name from Rundgren to Tyler. When she was in high school, Liv appeared alongside Alicia Silverstone in Aerosmith's 1994 "Crazy" music video, and they teamed up again professionally in 1998 when Steven's band contributed the rock ballad "I Don't Want to Miss a Thing" to her movie, Armageddon.

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Steven and Liv Tyler attend the Givenchy fashion show during Spring 2016 New York Fashion Week on September 11, 2015.
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Liv isn't mad at her mom for keeping Steven's identity a secret

Buell and Rundgren eventually split, though he still remained involved in Liv's life. She's explained that she grew up with "a nice, eclectic mix of parental figures," spending her childhood living between the homes of her mother, her grandmother (etiquette expert Dorothea Johnson), as well as with her aunt, uncle, and cousins in Maine.

Now, she considers both Rundgren and the Aerosmith singer to be her fathers. "I’m so grateful to Todd for choosing to be a father figure to me. It's a big thing for a man to say, 'I know this kid might not be mine, but I still want to be her father,'" she has said, adding she would visit Rundgren at Woodstock in the '80s. "Although he and my mom weren’t together, he was always a very stable, loving force in my life."

Liv holds no ill will toward Buell for keeping the secret from her either. "It's quite an emotional story, honestly, the whole thing," she shared in 2015. "My mother was very young when she had me and there was a little bit of confusion about where I came from, but I was very loved and very well taken care of by all my family, which was wonderful."

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Steven Tyler, Liv Tyler and Bebe Buell at the "Stealing Beauty" premiere in Los Angeles, California on September 7, 1996.
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Steven was even in the room when Liv gave birth to one of her daughters

Steven's also been an active part in the lives of Liv's children: Milo (with ex-husband, Royston Langdon), Sailor and Lula (with British sports agent Dave Gardner). In fact, Steven, along with her sister Mia, were present when Sailor was born six weeks early in 2015 and Gardner was on a flight. "I never expected to give birth with my sister and my dad in the room," she shared. "I called Mia and she came straight to the hospital, and she also called Steven. He walked into the room moments before Sailor was born, and cut his umbilical cord. It was wild."

Although her kids are close to all their grandparents, she said Steven isn't quite a typical grandfather: "He's very sweet, it's just so fun for him, for all the grandparents to get to play. He's amazing at making weird noises with his mouth, animal noises, a lot of animal noises! He's very playful and funny and lovely, he's kind of like a magical wizard he has things in his hair and all sorts of jewelry and he's just very fun."