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:

Lachey family social snaps
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Lachey family social snaps
CHEERS! With my family celebrating my NEW T.V. family #PeopleAreTalking! I am so excited to be joining #NBC this Fall to keep you ALL laughing every Friday night! #markpaulgosselaar #tonebell #breshawebb #djnash #willpacker #korinhuggins #pamfryman
"Excuse me Sir, I'd like diagonal lines in my grass please!" Ugh... It's so hard to find good help these days!
😍 Happy Father's Day! 😍
Happy Anniversary, Baby! We've done good! cam❤️bklyn
As the mom of two healthy children, Mother's Day this year will mean more than ever before. I'm thrilled to partner with @MarchOfDimes to help ensure that more families can live their dreams. So head to to read all about their #imbornto campaign and see how you can help all babies have a chance at a beautiful, healthy life ❤️ (link in profile)
My ❤️
#TBT Here is the inside of our 2013 Lachey family holiday card... Seems picture perfect, right? If you want a good laugh, head over to to see what was really happening behind-the-scenes and on the front of the card!
“Sending lots of love…from our family to yours!” #HappyHolidays See the full card on my site! I'm back and can’t wait to reconnect with YOU in 2015!
The Lacheys in Neverland! HAPPY HALLOWEEN!!!
Thank You @rhondadentphotography for capturing all the moments of Cam's 2nd Birthday! I'm so grateful you were there. I was so busy I didn't take one photo! #CamdensConstructionCrew
Sweet Home Cincinnati! I can watch Daddy and his little helper all day!
EVICTION NOTICE!!! Camden is officially out of his crib and in a big boy bed!!! In honor of his big transition, I want to share all the love and details that went into his sweet baby boy nursery. Head to and see all the photos (link in profile). 📷 by @rhondadentphotography
Had a blast taking Camden to meet Mickey for the first time. Thanks to our guide Abby for a great day!! #disneyland

RELATED: Vanessa and Nick Lachey Reveal They're Having a Baby Boy in Adorable Instagram Video

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!

WATCH: Nick and Vanessa Lachey Take Their Kids to Disneyland

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