The couple first announced they were expecting in February 2022, revealing the happy news just over a year after they confirmed they were dating.
"And suddenly my world would never be the same. Forever greater, forever expanded and deeper. Forever abundant and unconditional. Baby Boy July 4th (ish) 2022," Sharna wrote at the time.
She shared the news alongside a black and white portrait of hands cradling her growing belly, adding: "@brianaustingreen I love our family, I love that it's growing and I love you. How did we get so lucky."
In the months that followed the fit mum-to-be would share plenty of pregnancy updates, from her bump progress to her unlikely cravings.
Brian already has four other children from past relationships; Kassius, 19, with ex-fiancée Vanessa Marcil and Noah, nine, Bodhi, eight, and Journey, five, with ex-wife Megan Fox.
Though this isn't his first rodeo, the '90s heartthrob is clearly excited about becoming a dad again with Sharna.
"She's super responsible and she's super sweet and caring, passionate, fun to be around, so I feel blessed right now," he told Access Daily of his Aussie girlfriend in 2021.
At the time he joked that he went on a first date with her "begrudgingly" but it went so well that he had to see her again - and the rest, as they say, is history!
This article originally appeared on our sister site, TV WEEK.
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