Gwen Stefani "really, really" wanted a third child.

The No Doubt singer - who has sons Kingston, six and four-year-old Zuma with husband Gavin Rossdale - reveals she was desperate to expand her family in 2010, but "it didn't work out."

"I really, really, really wanted one about two years ago. It didn't really work out. So I feel good with what we've got. Everything works out how it should. You can't plan everything, right? You can try."

Despite her disappointment, Gwen is delighted with how well her children get along, despite constant fighting: "From the moment they wake up, they start beating on each other. I never knew they would be so physical. They're just starting to play real well together, but with a lot of fighting. They do look out for each other - especially the little one, he really loves his big brother."

However, Gwen's life is not all so easy and she admits her marriage has been hard work. "My biggest accomplishment is my marriage so far. Because it's hard, everyone knows it's hard. Marriage is something that I always wanted to do successfully. It was a dream of mine. I like the official-ness and the family-ness of it all, having the same name and making decisions together," she said.