Grace Margaret Wahlberg joins siblings Brendan, 16 months, Michael, 3 ½, and Ella, 6.
The Lovely Bones actor, 38, confirmed the pregnancy in October, announcing that Durham was expecting a girl.
Will the brood continue to grow now that Grace has arrived? That's up to his model wife, Wahlberg says.
"My wife is allowed to pick the magic number ... as many as she wants to have."
• Reporting by JULIE JORDAN
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