Jennifer Garner and Ben Affleck Name Son Samuel

By Sarah Michaud and Liz McNeil

02/29/2012 at 12:30 PM EST

Violet Anne, Seraphina Rose Elizabeth and ... Samuel.

Ben Affleck revealed the name of his and wife Jennifer Garner's newest addition – a son – Wednesday morning on his Facebook timeline.

"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.

PHOTOS: Jennifer Garner's Preppy-Chic Maternity Style

"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."

The couple, married since June 2005, announced the pregnancy in August.