Kidman confirmed the engagement with the rocker in a recent interview with Net-A-Porter's magazine The Edit, in which she was discussing her upcoming HBO series 'Big Little Lies'. Kidman said she already knew co-star Zoe Kravitz because she was once engaged to her father.
Kidman dated Lenny Kravitz a couple of years after her divorce from actor Tom Cruise in 2001.
She never disclosed an engagement, although she talked about a failed engagement in 2007 with an unnamed ex.
She's currently married to country singer Keith Urban.
In the interview with The Edit, about her connection to Lenny, Nicole - who has been married to Keith Urban since 2006 - said, "Well, I knew Zoë because I was engaged to her father. It's all in the family! I love Lenny, he's a great guy."
Meanwhile, Nicole previously admitted their relationship didn't last because the couple weren't "ready".
Speaking previously, she said, "It just wasn't right. I wasn't ready. We weren't ready."