Stephane Cardinale - Corbis/Corbis via Getty Mariska Hargitayreveals a family secret that she's been holding onto for three decades in a new documentary about her bombshell mom,Jayne Mansfield. TheLaw & Order: Special Victims Unitstar, 61, was in her 20s when she found out her biological father is Italian singer and comedian Nelson Sardelli, not bodybuilder and actor Mickey Hargitay, as she believed for much of her life. In new documentaryMy Mom Jayne, Mariska explores the tragic aftermath of the June 1967 car crash thatkilled Mansfield,a Hollywood movie star and sex symbol of the ʼ50s and ʼ60s, at just 37 years old. After her mother's death when Hargitay was 3, the actress was raised by Mickey along with her two siblings, Mickey Jr. and Zoltán. Mariska was later devastated to learn, however, that Hargitay was not her birth father, as she discusses in a new interview withVanity Fair. everett collection "He was my everything, my idol. He loved me so much, and I knew it," she said of Mickey. "I also knew something else — I just didn't know what I knew." Hargitay said she first confronted the truth in her 20s, when she was shown a photo of Sardelli. TheSVUactress instantly knew that he was her father. "It was like the floor fell out from underneath me," she recalls in the documentary. "Like my infrastructure dissolved." Mariska claims she confronted her dad, Mickey, about the revelation, but he denied it. She never brought it up to him again (Mickey died in 2006), but in 2004, when she was 30, she went to see Sardelli perform in Atlantic City and introduced herself. According to Hargitay, the singer burst into tears and told her, "I've been waiting 30 years for this moment." But the actress was chilly, channeling herSVUcharacter, she toldVanity Fair. "I wentfullOlivia Benson on him," she said. "I was like, 'I don't want anything, I don't need anything from you. I have a dad.'" Evan Agostini/Getty Explaining that she felt the need to be "loyal to Mickey," Hargitay detailed the struggle of coming to terms with "living a lie my entire life," admitting that she pondered about her place in either family. She eventually forged a bond with Sardelli and his daughters but also came to accept that "I grew up where I was supposed to." Want more movie news? Sign up forEntertainment Weekly's free newsletterto get the latest trailers, celebrity interviews, film reviews, and more. "I'm Mickey Hargitay's daughter —thatis not a lie," she added, tearfully. "This documentary is kind of a love letter to him, because there's no one that I was closer to on this planet." The actress, who has two adopted children with husband Peter Hermann, said the whole ordeal has helped her in her own journey as a parent. "They aremykids," she said. "Now I understand so much, and, boy, is it sweet." My Mom Jaynemarks Hargitay's debut as a documentary director. The emotional film had its world premiere at the Cannes Film Festival on Saturday and is set to have its TV debut June 27 on HBO. Read the original article onEntertainment Weekly