Jimmy Kimmel and Molly McNearney. Picture: Bang Showbiz

Jimmy Kimmel has admitted neither he nor wife Molly McNearney wanted to get too attached to their baby son Billy after he was born with a congenital heart defect because they were worried about what would happen to him.

The 50-year-old presenter's little boy Billy underwent open heart surgery just three days after he was born last May and he admitted he and his wife Molly McNearney weren't initially open with their feelings about the situation, but realised after the tot had undergone a second surgery they had shared the same fears.

He told Oprah Winfrey in an interview for her O, The Oprah Magazine: "There were secrets we kept from each other that we revealed only after the second surgery.

"The biggest one was that, I think subconsciously, we didn't want to get too close to the baby, because we didn't know what was going to happen...I don't know if that's right or wrong or common or uncommon. 

"But when I told her I was feeling that way, she said, 'Oh, I'm so happy you said that because I was feeling that way too, and I didn't want to express it.' "

After having surgery, Jimmy - who also has kids Katie, 26, and Kevin, 24, with former wife Gina, and three-year-old Jane with Molly - revealed Billy is now doing "great", though he will still require further treatment.

He explained: "He'll have another surgery when he's around six or seven years old, but in the meantime, he's doing great."

Jimmy recently joked little Billy is doing so well, his capabilities are far beyond what is typical for a baby.

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Speaking ahead of his second surgery, which took place in December, he quipped: "He's doing great. Young Billy made his first visit to our office today. He's juggling. He's translating Flaubert from French into English. He's really an amazing kid. 

"No - he smiles. That's pretty much it. He is very interested in ceiling fans. He likes those a lot. I could get him to pay the same amount for Netflix just to watch ceiling fans."