Kardashian and Scott Disick welcomed the newborn on the same day that the baby's gender was set to be revealed on the latest episode of "Kourtney & Khloe Take the Hamptons."
The baby boy, whose name and weight haven't yet been shared with the media, joins brother Mason, who celebrated his fifth birthday on Sunday, and sister Penelope, two years old.
"The family is freaking out with joy," an anonymous source told E! News. "What an amazing coincidence."
Kardashian recently posed nude for magazine DuJour Magazine.
"To me, nudity is not something to be ashamed of," she told the magazine. "I'm not embarrassed of my body. I'm at my best when I'm pregnant. It's such an amazing feeling, the transformation that your body goes through."
Kardashian was featured on the cover of the latest issue of the magazine Fit Pregnancy.
"I'm not getting a baby nurse," she said of her upcoming challenge of managing three little ones at home. "I take two months off and no one is allowed to bother me or talk to me about anything work-related -- or maybe three months this time."
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