"Magical moments yesterday... Nicole and I would like to introduce Beckett Richard Phelps to the world! We had a healthy baby boy and a healthy mama," Phelps wrote. "I truly do feel like the happiest man in the world. Being able to build our family to now 4 (6 with doggies) is so incredible! #familyof4now."
Even their little boy Boomer got in on the celebrating. The parents posted a photo to their son's personal Instagram account -- which is adorably written from Boomer's point of view -- to commemorate the occasion.
The precious photo shows Michael holding his newborn son as Boomer sweetly stares at him in fascination.
"I am officially a big bro!!! All I wanna do is hold him," the caption reads. "I can’t wait til I get to teach him so many cool things about the world!! #bigbro."
Fans were speculating that the couple were getting ready to welcome a baby girl, due to the famed swimmer and expect father's choice of a pink button-down shirt. However, that speculation clearly proved to be wrong.
"We always talked about three, so the second one is on the way. We’ll see what happens," he said. "We’re going man-to-man now, and it’s probably going to be more challenging. Boomer is at the point now where he’s running all over the place."