updated 02/29/2012 AT 12:00 PM ET
•originally published 02/29/2012 AT 12:30 PM ET
“We are happy to announce on February 27, Jennifer gave birth to a healthy baby boy, Samuel Garner Affleck,” the actor, 39, writes.
The newborn, who arrived Monday, joins his elder sisters, ages 6 and 3 respectively.
“Our girls are working on names. At first they were definitely Disney. It was like, Donald Duck, Minnie Mouse Affleck, the actress, 39, told Jay Leno recently. “And then they’ve moved on. Then it was Peter Pan, Captain Hook, Smee.”