The Willis' rep had no comment on the family's happy news.
After tying the knot in 2009, Willis and the model turned designer welcomed their daughterMabel Ray, now 20 months.
"I'm happier than I've ever been. I'm changing diapers like a champ," the actor told Zoomer in June.
"What I've also discovered is how much love I feel for our baby. I think I'm even more open and more giving as a father now. I pay more attention now because I value it more and I'm less caught up with my career."