Mabel is the first child of the couple, who got married in March 2009. Bruce, 57, has three daughters - Rumer, 23, Scout, 20, and 18-year-old Tallulah with ex-wife Demi Moore. Willis had previously claimed that he was indifferent to having children with Emma, 33, as the only thing that mattered was being with her.
"I'd like to have a thousand more children, or zero more children. It doesn't matter. Emma makes me feel great," showbizspy.com quoted Bruce as saying.
"I'm the happiest, I've ever been and this comes after a long period of being kind of lonely, even though I tried to convince myself I was enjoying my life. Before I met Emma I was very pessimistic about finding that special woman with whom I would want to spend my life with.
"I thought it would be difficult for someone like me, who is well known, to find a woman who didn't have an agenda and who just wanted to be with me because they loved me, pure and simple," he added.