#BabyShark is finally here!

Michael Phelps and wife Nicole announced the birth of their second child, son Beckett Richard on Instagram Tuesday. The couple shared that their baby boy was born on Monday, Feb. 12.

The new addition joins 21-month-old big brother Boomer.

“Magical moments yesterday… Nicole and I would like to introduce Beckett Richard Phelps to the world! We had a healthy baby boy and a healthy mama,” the 28-time Olympic medalist, 32, captioned a photo of Nicole and Boomer cradling the newborn.

“I truly do feel like the happiest man in the world. Being able to build our family to now 4 (6 with doggies) is so incredible! #familyof4now,” he added.

Want all the latest pregnancy and birth announcements, plus celebrity mom blogs? Click here to get those and more in the PEOPLE Babies newsletter.

New mom Nicole also shared the baby news on social media. “Our family grew by 1 yesterday meet Beckett Richard Phelps. I’m surrounded by boys and I couldn’t be happier,” she wrote.

RELATED GALLERY: 50 Aww-worthy Pics of Michael Phelps’ Baby Son Boomer

For more coverage, follow our babies magazine on Flipboard.

And even Boomer proclaimed his new older sibling status on his Instagram page.

“I am officially a big bro!!! All I wanna do is hold him! I can’t wait til I get to teach him so many cool things about the world!! #bigbro,” the adorable photo of the three Phelps boys read.

In August, the couple announced in matching social media posts that they are expecting again.

“Number 2 on the way!!!! So excited!! Wonder if it’s a boy or a girl??” Phelps wrote alongside a photo of Boomer clutching a pregnancy test while snuggled up in his mom’s arms.

Phelps and the former Miss California USA welcomed Boomer in May 2016. They wed later that year – twice! First, the pair tied the knot in June, and then again in late October during a larger event in Cabo San Lucas, Mexico.

Phelps previously revealed to PEOPLE that his wife was looking forward to growing their family, sharing, “Nicole has recently brought up that she would like a girl!”

“We definitely want more kids, it just depends on when. I’m sure I’m getting pressure” he said, teasing, “ trying to get moving on some things!”

Adding, “We’re going through life every day happy and blessed with what we have. But I hope to have more kids in the future.”