The pair - who married in July 2001 - already have five-year-old Francesca Nora.
Jason previously revealed his wife helped him turn his life around after he became a heavy drinker and wild partygoer.
He said: "Meeting my wife Amanda was the best thing that could ever have happened to me. She wasn't going to let me screw around my life anymore, so I stopped drinking and started behaving like a decent human being.
"Then I got very, very lucky when 'Arrested Development' came along. That series saved my career - it gave me back my credibility I used to have when I was much younger and before people gave up on me as a party guy in Hollywood. It was just enough to make me ambitious again."
