The newborn was greeted on Monday by actors Facinelli, 48—best known for his role in the Twilight movie series—and Harrison, 33—most recently seen in The Vanished.
The couple's first kid together is this one. Luca, 25, Lola, 19, and Fiona, 15, are the three former children Facinelli had with his ex-wife Jennie Garth.
The caption on Harrison's photo said, "Not a burrito tummy," and it showed Harrison with the beginnings of a baby bulge.