The '13 Going On 30' actress is currently pregnant with the couple's third child and while the actor initially wanted their two daughters to have a baby brother, now he isn't convinced.
She told Jay Leno: "I would have thought [he wanted a boy]. At first I think I really thought so. And then he kind of said, 'Well, we have girls. We know how to do girls. My girls love me. I'm the big guy in the house.' So, now I'm not sure."
Jennifer - who knows the sex of the baby - says the couple's daughters, Violet, six, and three-year-old Seraphina, want to name the baby but she isn't sure about their choices.
She said: "Our girls are working on names. At first they were definitely Disney. It was like, Donald Duck, Minnie Mouse Affleck. And then they've moved on. Then it was Peter Pan, Captain Hook, Smee.
"They're coming up with lists and coming in and saying, 'Let's have a baby-naming contest! Let's have a baby-naming poll!' They ask everyone, because they just want to know. But we're not telling."