Nick and Vanessa Lachey welcome third child on Christmas Eve -- find out his name!

It's a party of five!

Nick and Vanessa Lachey got a very merry holiday surprise when their third child decided to make an early entrance into the world on Christmas Eve.

WATCH: Vanessa Lachey Radiantly Flaunts Baby Bump While Celebrating Her Birthday With Girlfriends

Vanessa, 36, gave birth to son Phoenix Robert Lachey on Saturday. The proud parents shared the good news with fans via Instagram on Monday, with both posting the same sweet photo of their newborn holding onto his mom's hand.

The pair announced that they were expecting again in September and revealed baby No. 3's gender last month. Nick, 43, and Vanessa are already parents to 4-year-old son Camden and 23-month-old daughter Brooklyn.

See photos of the couple together:

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Judging from the actress' social media posts, Christmas is a special time for Vanessa. She's been posting lots of adorable snaps of her growing brood over the last few weeks, including Camden sending a letter off to Santa, Brooklyn adorably sitting on her dad's shoulders as they braved the snow, and some of the decorations at her home (including peeks at the baby bump!).

Congratulations to Nick and Vanessa!

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