Kimmel revealed his son's health scare during an episode of Jimmy Kimmel Live!, where he broke down in tears recalling that a few hours after Billy was born, a nurse noticed he was "purple" and doctors diagnosed him with a heart defect.
"Six days after open heart surgery, we got to bring him home, which was amazing," said Kimmel, revealing that Billy will have to have two more procedures on his heart later in life. "He's doing great. He's eating, he's sleeping. He peed on his mother today while she was changing his diaper. He's doing all the things that he's supposed to do."
Last week, Kimmel told ET's Kevin Frazier that Billy's second heart surgery might be happening soon.
Hear what he had to say in the video below.