The baby weighed in at 6 pounds, 2 ounces at birth Oct. 27, the magazine said Sunday.
"He is a beautiful, healthy baby boy. Everyone is so excited and happy," a source told E! News. "Emile showed up after the baby was born and he is spending time bonding with his new child."
People.com said Hirsch and the infant's unidentified mother are not in a romantic relationship but are friends and plan to raise the baby together.