Rose Byrne and Bobby Cannavale reveal they welcomed baby boy a week ago

Julie Delahaye

Rose Byrne and Bobby Cannavale have surprised fans after revealing they welcomed a baby boy at the beginning of February. Although the couple didn't share their happy news at the time, Bobby, 45, made the announcement during an appearance on The Late Show with Stephen Colbert on Saturday.

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Rose Byrne and Bobby Cannavale have welcomed a baby boy

"I had a baby on Monday, yes," the actor told Stephen, revealing the newest addition to his family was born on the first day of the month. "You know, I didn't do anything. We [men] don't do anything and I'm so tired."

Bobby also opened up about his first week of fatherhood, and shared the biggest change he has noticed over the last few days.

"I think I've gained 28 pounds since Monday," he said. "I mean, I'm not kidding you. Like, this jacket fit so well, like, last Thursday. But I've been eating so much."

The Blue Jasmine star also delighted fans when he revealed the couple have named their little boy Rocco, adding that his son "is doing great".

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This is the couple's first child together

Speculation that Bobby and Rose were expecting their first child together first arose in October, after Rose was spotted walking through LAX airport with a hint of a baby bump. That the new parents kept the news of their new arrival secret is not surprising – they are notorious for being extremely private.

Despite being together since 2012, they didn't announce their relationship until 2013, when Bobby confirmed they were dating during his Emmys speech.

He said: "And I want to thank the love of my life, Rose."

Rose, 36, has since opened up about her love life, admitting that she's "trying to get better at romance".

"To be honest, I'm not naturally that much of a romantic person – Australians don't like making a fuss," she told ELLE Canada. "I have trouble with things that feel very manufactured, like Valentine's Day."

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