The 'I Want It That Way' singer became a first-time father on Tuesday, 19 April when wife Lauren Kitt welcomed a baby boy at their home.
He's been named Odin Reign Carter.
According to Nameberry, Odin was the "name of the supreme Norse god of art, culture, wisdom and law - who was handsome, charming and eloquent into the bargain."
Lauren was in labour for 30 hours before delivering Odin via a water birth, according to Entertainment Tonight, which was first to confirm the birth. He weighed 8lbs 11oz.
Nick married fitness expert Lauren in 2014 following a romantic proposal on a cliff top in the Florida Keys at sunset. Their relationship was the focus on a VH1 reality show called I Heart Nick Carter.
The couple announced Lauren's pregnancy in October, making Nick the fifth and final member of Backstreet Boys to become a father.
Brian Littrell is dad to son Baylee, Kevin Richardson has sons Mason and Maxwell, AJ McLean is father to daughter Ava, and Howie Dorough has two boys, James and Holden.
The boys have been congratulating Nick via Twitter, with Brian saying: "My how time flies..... 23 years ago today, I met #nickcarter and he was 13...... Now he is a new member of an elite club.... #fatherhood......#BSBDAD.... Congrats to the Carter Family...."
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