The 42-year-old actor revealed as much in an interview with Access Hollywood on Wednesday. Duhamel and the 39-year-old Black Eyed Peas singer are already parents to son Axl, and the star told host Kit Hoover the couple's successful marriage is based on fun.
"I would say it's working because we have a lot of fun," he said of their partnership. "I genuinely like her! She likes me, you know? I'm nobody to give advice on relationships, but for whatever reason, we just really like each other."