Co-host Jackie O said she was "so happy" for the couple, noting that the news explained Kyle's emotional outbursts of late.
Eerily, Kyle also revealed that KIIS FM resident psychic Georgia Walker actually predicted that Kyle and Tegan would be expecting in the near future.
The pair also announced they were expecting a boy after hosting a grand gender reveal on a boat, complete with planes flying over with blue smoke.
"Baby Sandilands is a….. BOY!! Congratulations Kyle and @tegankynaston on your little prince!" the KIIS FM Instagram page announced.
Kyle has previously hinted at wanting children with Tegan, recently telling the Daily Mail Australia that the pair had been given the green light following fertility tests.
"I was really nervous [about the fertility test] until it came back saying, 'Yep, it's all great, everything's fine.'
"[Tegan] is all good, obviously. She's a young and healthy woman. So it's good to know that everything's fine in that area so it won't interfere with any future plans.
"[I wasn't thinking about kids] because I've been work-focused. But all my friends have kids and Tegan's family and friends, they've all got kids. And we're like the only couple at the barbecue that've got no kids, we have the FOMO [fear of missing out]."
WATCH: Kyle Sandilands proposes to Tegan Kynaston (Article continues after video)
The exciting news comes after Kyle popped the question to Tegan during a holiday at his house in Port Douglas earlier this year.
"She said YES!!!! 💍 Congratulations Kyle & Tegan!!! ❤️#KJShow," a post to The Kyle and Jackie O Show's Instagram read, along with a photo of Kyle and Tegan and her sparkling ring.
The engaged couple were quick to receive many well wishes from fans and famous friends, including American columnist Perez Hilton who wrote: "Amazing!!! Congrats!!! 👏👏."
The account also shared a sweet video of the moment Kyle got down on one knee, complete with water views, a red carpet, candles, and even fireworks.
Kyle spoke about the proposal live on air, admitting that a few things went wrong, including that Conrad Sewell was supposed to perform their favourite song, but the singer had to pull out at the last minute because he'd contracted COVID.
Despite the last minute changes, Tegan was overcome with emotion at the surprise. As was Kyle, who admitted he got teary during the proposal.
As for their wedding plans, Kyle confessed there is no official date yet, but the ceremony will likely be in Sydney.
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