Rose Byrne and Bobby Cannavale are officially parents!

Cannavale announced the arrival of his son on his The Late Show with Stephen Colbert appearance on Friday night.

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Baby Rocco was born on Monday to Byrne, Cannavale's partner since 2012.

"I'm so tired. I think I've gained 28 pounds since Monday," the 45-year-old Vinyl actor joked.  'I'm not kidding, this jacket used to fit so well but I’ve been eating so much!"

Cannavale's famous friends are already giving gifts to celebrate the little' guy's birth -- he told Colbert that actor Al Pacino gave them an always-useful diaper cake to celebrate Rocco’s birth

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Rocco is the first child for 36-year-old actress Byrne, and the second for Cannavale. His eldest son, Jake Cannavale, is 20 years old -- an age difference that prompted Colbert to joke "nice grouping."

Bobby can be seen next in Vinyl, which debuts on HBO on Feb. 14th.