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The actor welcomed his first child, a boy, with his wife, writer and TV host Dawn O'Porter, on Sunday, Jan. 25, her rep confirms to PEOPLE.

"It's a boy

[Dawn] & I would like to introduce Art, our gorgeous baby. Well, I'm pretty sure he's ours," O'Dowd joked via Twitter, sharing a mashup photo of a baby sporting his beard and his wife's haircut.

Added O'Porter, "Thanks all. He is one week old today. It's been a beautiful week. I think we'll definitely keep him."

O'Dowd, 35 - who wed O'Porter, 36, in August 2012 - announced his wife's pregnancy while participating in the ALS Ice Bucket Challenge in August. After being showered with the cold splash, the dad-to-be nominated his unborn baby - a challenge completed when O'Porter poured water on her belly.

Known for his roles in Bridesmaids and on The IT Crowd, O'Dowd is currently appearing in St. Vincent and will next star in Icon, scheduled for release in August. His first children's book, Moone Boy: The Blunder Years, based on the TV series, will be released in the U.S. in May.

him: It's a boy! @hotpatooties & I would like to introduce Art O'Porter, our gorgeous baby. Well,I'm pretty sure he's ours

Her: Thanks all. He is one week old today. It's been a beautiful week. I think we'll definitely keep him;) The 'Bridesmaids' star met Dawn through mutual friends at her 30th birthday party and wed the brunette beauty in a low-key ceremony in June 2012, when she decided to change her surname, Porter, to O'Porter, to acknowledge their nuptials formally.

Dawn previously revealed she would be giving birth to their first child in Los Angeles because it is where they currently live, despite neither of them being from America.

She said: "We're having our baby in America definitely, but I don't know where we're going to be living in five years. It's nice that we travel all the time and we love living in LA. That's totally home. But London or Ireland is also another opportunity."

7:39 PM - 1 Feb 2015

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