The 49-year-old actress has been notoriously tight-lipped on her more than decade-long marriage to Cruise, which ended in 2001. But in a candid new interview, Kidman says she can't believe she married Cruise at just 23 years old, after the two met on the set of 1990's Days of Thunder.
"I was so young when I got married," Kidman acknowledges to Red magazine. "I look back now and I'm like, 'What?'"
Still, the Oscar-winning actress has no regrets -- even when she compares herself to celebs these days.
"You look at Taylor Swift, I mean how old is she? She's 26. I had two kids by the time I was 27 and I'd been married for four years," she says. "But that's what I wanted."
Kidman eventually remarried, tying the knot with country star 48-year-old Keith Urban in 2006. The two are one of the most romantic couples in the business, and the Australian star says she's learned a lot about maintaining a marriage the second time around.
"When you're older, you've been through things, you've made mistakes," she explains. "So, you come into it [a second marriage], still giddy, but wanting it to last. We always consider the 'us.' We say, 'Is this going to be good for us?' It's the simplest phrase, but it works."
Of course, she admits that her relationship with Urban hasn't always been the smoothest. But these days, the couple -- who celebrated their 10th anniversary in June -- are "stronger than ever."
"It was really up and down for the first three months," Kidman shares. "We've been through a lot for ten years. And we're stronger than ever. I say that while touching wood, and no way in a boastful way. I just say it with wonder -- absolute wonder."
Kidman has two daughters with Urban, 8-year-old Sunday Rose and 5-year-old Faith Margarat, who was born via surrogate. She also has two children she adopted with Cruise, 23-year-old Isabella and 21-year-old Connor.
"My husband says I'm 'deeply maternal,'" she notes. "I like to take care of people. It brings me a lot of joy."
"Motherhood is about the journey," she adds. "There are going to be incredible peaks and valleys, whether you are an adopting mother or a birth mother. What a child needs is love."
"Just want it more than anything," Urban said. "That's it, isn't it?"
"Yeah, prioritize it," Kidman echoed. "Also, as much as we love each other, we really like each other. I'm speaking for myself, but that is a huge part of being married. Always, the first person I want to share anything with is him. It's true."