David, 47, also shared the exciting news with his Instagram followers, posting a photo of himself holding their son who was resting comfortably in one arm.
"I got the best #valentines #day Present!! Mama is a master at baking these! I’m a lucky dude! Welcome to the world Axel! 2/14/20."
Congratulatory comments quickly flooded in, with longtime pal and Brooklyn Nine-Nine co-star, Stephanie Beatriz, writing, "So happy for you & your beautiful family!!! You're a badass!"
Ant-Man actor, Bobby Cannavale also responded: "Beautiful. Congratulations to you and David and Enzo!!!"
"Ohhhhh how BEAUTIFUL," Diana Maria Riva also added. "Congratulations lovely mama!!!"
The couple— who are already parents to 3-year-old, Enzo Fumero— announced they were expecting their second child on November 18.
“Oh yeah, I’m hella pregnant,” the beloved Gossip Girl alum captioned an Instagram photo which showed off her bulging baby bump.
“To be honest, I haven’t felt like posting about it because this pregnancy has been way harder and… I don’t feel that cute? But yesterday I got a really intense massage, an awesome chiropractic adjustment, and my hair feels thicker… so I feel a little bit cute today," she continued, adding that she and her husband are gearing up to welcome another boy.
Melissa and David met on the set of the soap opera, "One Life to Live", which they both starred on in the early 2000s. They eventually tied the knot in December 2017.
During Melissa's first pregnancy, Brooklyn Nine-Nine showrunners worked her baby bump into the plot, having her character go undercover at a women's prison as a pregnant inmate. After changing the script, Melissa chatted to Entertainment Tonight about how the timing of her pregnancy lined up perfectly with her shooting schedule.
"So we got a surprise pregnancy that weirdly timed out brilliantly where my due date was two weeks after we're supposed to wrap Brooklyn Nine-Nine," she said.
"So we felt like, 'OK this is meant to be. This feels very serendipitous.' We were, after we got over our initial shock, we were very, very excited."