The 40-year-old actor is expecting his first child with Black Eyed Peas' singer, reported Contactmusic.
"You know your kid is going to get - he's going to fall and bump his head. And he's going to do all of those things," he said.
Duhamel said he feels the timing is right for him and Fergie, 37, to have children as they feel much 'wiser' than when they first wed in 2009.
"Now I get to relive my youth through my child and see my child live all that. So everybody's got a different path," he added.