Kourtney Kardashian’s son Reign, 10, reacts to wild rumor Justin Bieber is his dad

Not his “Baby.”

Kourtney Kardashian’s youngest son, Reign Disick, shut down speculation that his real father is Justin Bieber — and not Scott Disick.

The 10-year-old appeared on a recent Instagram Live with his stepsister Alabama Barker’s boyfriend, Scooter Jackson, and responded to a fan who asked about the wild paternity rumor.

“No! He’s not, bro, I swear,” Reign said of Bieber. “Justin Bieber’s not my dad. Scotty, Scotty, Scotty is my dad.”

The preteen added, “I don’t know how old my mom was, but I think Justin Bieber was 16 when I got born [sic]. Yeah, I don’t think my mom would do that.”

The “Baby” singer, 31, and the “Kardashians” star, 45, were romantically linked in 2015, shortly after she split from Disick, 41.

A source told Page Six at the time that the two were seen partying together at a lounge in Los Angeles.

“Justin and Kourtney were nearly inseparable,” the insider spilled. “They were smoking on the patio together and were super touchy-feely.”

The source insinuated Kardashian had been entertaining Bieber to make Disick jealous, explaining, “Kourtney knows it upsets [Scott], so when Scott flaunts being out with other girls, she hangs out with Justin to get back at him.”

Neither the Poosh founder nor the “Yummy” crooner publicly addressed their rumored fling at the time.

However, Bieber later joked about feeling “used” by Kardashian.

“I’m being used, man. What can I say? No, no, but for real, she’s great. I’ve known [the family] for years,” he said on “The Bert Show” in 2016. “We’ll leave it at that.”

Kardashian shares three children — sons Mason, 15, and Reign and daughter Penelope, 12 — with Disick. The two dated on and off from 2006 to 2015.

The Lemme creator also has a 1-year-old son, Rocky, with her husband of nearly three years, Travis Barker, while Bieber and his wife, Hailey Bieber, welcomed a son, Jack, last August.