Pete Wentz has hinted he and wife Ashlee Simpson are expecting twins.The Fall Out Boy rocker accidentally let the news slip during an interview on a US radio show when he referred to his unborn baby as "them".Pete said: "We've been keeping a book so far, like a journal for them - for them when they're, uh, born."The 29-year-old musician then started laughing nervously before wrapping up the interview.Meanwhile, Pete has also revealed he is keen to find out the sex of the unborn child, or children.He said: "I'd like to know the sex of the baby. It would be a bummer if you bought a boy a bunch of pink stuff!" He also revealed 23-year-old Ashlee is coping well with the pregnancy, adding to In Touch Weekly magazine: "I think any pregnant woman knows it's a lot of stress on your body, but she's really healthy and handling it like a champ."

Pete and Ashlee married in May after dating for two years.