Johnny Galecki and Girlfriend Alaina Meyer Welcome Son Avery: 'Full and Grateful Hearts'

Johnny Galecki is taking on a new role after the end of The Big Bang Theory: first-time dad!

The actor, 44, and his girlfriend Alaina Meyer announced the birth of their son Avery on social media Wednesday, sharing a sweet photo of their newborn's hands.

In the snapshot, Galecki's hand gently grasps his son's, while Meyer, 22, holds onto their baby boy's other hand.

"With full and grateful hearts we welcome our beautiful Avery into this incredible world," Galecki captioned his version of the image, in black and white. "Thank you for all of your love and support. ❤️❤️❤️"

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The couple first announced that they were expecting back in May.

"We are absolutely over the moon to announce that we will soon be welcoming a little one into this crazy and wonderful world," the couple told PEOPLE. "There truly is love out there for all. We hope ours is the ember of yours, as we feel yours is the ember of ours."

Galecki and Meyer shared that they were having a boy that same month with a blue-themed "gender reveal party."

"A day I'll never forget," The Conners actor wrote, posting a photograph of himself and his girlfriend covered in blue paint after the reveal.

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Galecki previously said he had been hoping for a girl, explaining on The Talk in May that he'd even painted his nails pink to try and encourage it.

"I get a little bored looking exactly the same way for nine and a half months every year playing Leonard," he said of his Big Bang character. "So we wrapped and I threw some blue in my hair, then I got superstitious that I was manifesting a boy, when I kind of prefer a girl."

"Don't play this tape for my child years from now!" he joked, also noting that he actually valued his baby's health most of all at the end of the day.

The couple first went public with their relationship in September 2018 by posting an Instagram photo from a night out together.

Since announcing the pregnancy, they kept busy documenting how they prepared for baby Avery. Galecki shared a photo in October of the book he was reading, The Expectant Father, with the hashtag "#sundayreading."

Meyer showed off pictures from her baby shower that same month, where she revealed the name the couple had chosen for their son by displaying large silver balloons to spell "AVERY."

"I am so grateful for the sweetest, most amazing night, celebrating Avery. Can not wait to meet this little man, only 4 weeks left ?" she wrote.