The brunette actress has always said she wants a big family but Douglas is happy with their children, son Dylan and daughter Carys, and thinks his wife would be just as happy focusing on her work.
He told Britain's Night and Day magazine: "I think Catherine is resigned to that fact now. She's gone back and forth on the subject, but when she gets back into work, I think she realises two's enough and I say to her, 'Just think of your stepson as your third child.'" Douglas, 61, has a 27-year-old son, Cameron, from his first marriage to Diandra Luker. Cameron is just nine years younger than Zeta-Jones, who is 36.
The Oscar-winning actor also claims he has become a "Mr Mum" and is happy to stay at home and look after the children so his wife is able to go and make films.
Douglas is currently starring in 'You, Me and Dupree' and 'The Sentinel' which are both out this summer.