The 36-year-old actress has two sons, 12-year-old Ryder with ex-husband Chris Robinson, and four-year-old Bingham with former fiance Matt Bellamy, and while she loves every second of parenthood, Kate can't believe the kids running around at home are hers.
"There are sometimes when I'm like, 'Do I really have two kids? I have two kids!'" she laughed during an interview on U.K. TV show Lorraine. "No, I really love being a mother."
Asked if she'd like to have more in the future, Kate replied: "I'd have six kids. I think I've always thought I'd have four but who knows? You never know!"
Kate's most recent film sees her voice the character of Mei Mei in Kung Fu Panda 3. It's one of only a few of her movies suitable for her sons to watch, and she was thrilled to be able to share the project with her boys.
"Bing is at the age where it's fun, it's here and then it's gone. Ryder can actually see it, understand it and enjoy it - Ryder grew up with the Kung Fu Panda movies," she said. "It was really cool to share it with Ryder and he got to walk the red carpet in LA with me."
Working on an animated film has its benefits, but also means Kate doesn't get to actually work alongside her fellow actors. However, she hopes to be able to collaborate with her co-stars again on a future project in which they would actually be able to share the screen in person.
"We only see each other promoting," she said. "I'd love to work with Bryan Cranston, Angelina Jolie, I didn't even get to work with Jack Black. Everybody goes, 'He's so funny', and he is really funny but he's also just so lovely."