People confirmed the news with the 41-year-old entertainer, who is over the moon.
"It's always been my dream to be a mother and I'm so happy that Carter and I found each other," the new mom told the magazine. "We are so excited to start our family together and our hearts are exploding with love for our baby boy."
Hilton announced the arrival of her son on Instagram with a photo of his little hand in hers.
“You are already loved beyond words 💙,” she wrote.
Celebrity friends showered Hilton and Reum with well wishes and congratulations, including Kim Kardashian, Chrissy Teigen, Heidi Klum, Demi Lovato, Kris Jenner, and Lindsay Lohan.
Teigen, who just welcomed her baby girl Esti, commented, “a BABY!!!!! congratulations so happy for you both!!” Kardashian added, “So happy for you guys!!! 🤍”
"We knew we wanted to start a family, and I was like, 'This is perfect timing. Usually I'm on a plane 250 days out of the year, and let's just get all of the eggs stocked and ready,'“ Hilton told People last month.
Reum, a venture capitalist, also shares a 10-year-old daughter with former reality star Laura Bellizzi. And Hilton’s sister, Nicky Hilton Rothschild, welcomed her third child, a son, who joined big sisters Teddy, 5, and Lily-Grace, 7. So lots of Hilton cousin fun ahead!