Jennifer Garner gave birth to her third child, a son, in Santa Monica, Calif., a source close to the actress told UsMagazine.com Tuesday. No other details about the baby\'s birth were immediately available. Garner is married to writer-director-actor Ben Affleck. They have two daughters, Violet, 6, and Serafina, 3. UsMagazine.com said Garner\'s publicist did not respond to its requests for comment.