Jenna Dewan and Steve Kazee welcome son Callum Michael Rebel

By Good Morning America

It's a boy for Jenna Dewan and Steve Kazee!

The actress gave birth to her first child -- son Callum Michael Rebel Kazee -- with her fiancé on March 6, she announced on Instagram.

Dewan also has a 6-year-old daughter, Everly, with her ex-husband, actor Channing Tatum.

"And just like that, our hearts exploded into all of eternity and beyond," Dewan captioned an image of her holding the newborn. "Welcome to the world you little angel!"

Kazee added in a post of his own: "In an instant our universe burst wide open and nothing would ever be the same. Welcome to earth star child."

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And just like that, our hearts exploded into all of eternity and beyond ❤️🌈❤️ Welcome to the world you little angel! ❤️ Callum Michael Rebel Kazee 3/6/20

A post shared by Jenna Dewan (@jennadewan) on Mar 10, 2020 at 11:28am PDT

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In an instant our universe burst wide open and nothing would ever be the same. Welcome to earth star child. Callum Michael Rebel Kazee 3/6/20

A post shared by Steve Kazee (@stevekazee) on Mar 10, 2020 at 11:28am PDT

Dewan, 39, and Kazee, 44, began dating in 2018 and announced last September that they were expecting a baby. Kazee, a Tony Award-winning actor, proposed to a Dewan a few months later.

"A lifetime to love and grow with you...you have my heart," Dewan wrote on Instagram in February.

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Well...the news is out. I can’t even begin to describe the feelings that I have had since we first learned that Jenna was pregnant! I have waited my entire life for this moment and couldn’t have found a better person to build a family with. The past year and a half has brought so many things into my life that have filled me with the deepest of gratitude. A partner who radiates love, warmth, and kindness. A partner who has faced some of the hardest moments life can deal you with grace, humility, and a desire to learn from the ups and downs. A partner who is continuously growing from those lessons and who supports my growth as a person with love, unwavering support, and understanding. Jenna also brought with her one of the greatest gifts one could ever imagine...her beautiful daughter. Evie burst into my life like a supernova and has continued to burn so brightly in it. I have learned so much about parenting already from watching how amazing Jenna is with her and Evie has taught me so much about what it means to love and communicate with a child and I can’t wait to give her a sibling and make our little family a little bit bigger.

A post shared by Steve Kazee (@stevekazee) on Sep 24, 2019 at 4:54pm PDT

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A lifetime to love and grow with you...you have my heart ❤️

A post shared by Jenna Dewan (@jennadewan) on Feb 18, 2020 at 7:00pm PST