Prego Kourtney Kardashian demands baby daddy marry her – now!

Kourtney Kardashian locked in a marriage showdown with her baby daddy.

With her famous family behind her, the 30-year-old reality star is pressuring her on-again, off-again beau Scott Disick, 26, to marry her before their love child arrives in late December, say sources.

"Kourtney not only wants a wedding, she’s demanding it," explained an insider.

The Kourtney & Khloe Take Miami star is using her sisters Kim and Khloe, as well as mom Kris and stepfather Bruce Jenner to help pressure Scott, added the source.

"Scott is hemming and hawing, trying to buy himself more time. He’s suggesting they wait until after the baby arrives to discuss wedding plans, but Kourtney wants to lock Scott down," divulged the insider.

"She’s informed him that she’d be happiest with a no-frills wedding over Thanksgiving, and that her mom and sisters would handle all the planning."

Kourtney has publicly stated: "We should do everything for the baby right now, and I’ll worry about myself later."

But privately she’s "insisting on a guarantee that she and Scott will bring this child into the world as a committed family unit," the source revealed.

Kourtney announced on the Today Show on Aug. 13 that she and ex-boyfriend Scott – whom she’d split with at the beginning of the year – had rekindled their romance and were expecting a baby.

While Scott has moved into her Calabasas, Calif., home, some members of the Kardashian clan still have serious doubts about him.

Mom Kris expressed her disapproval of Scott on multiple episodes of Keeping Up with the Kardashians.

And Scott reportedly cheated on Kourtney a number of times, something she hinted at when she told a reporter: "When he was with me, I would trust him. I just didn’t like his behavior when he would go to New York and hang out with his friends and party all night."

As The ENQUIRER exclusively reported, the night before Kourtney made her surprise pregnancy announcement, Scott partied like a carefree bachelor at an art show in Los Angeles.

Despite all that, "Kourtney has made it clear to Scott that if she’s having his baby, she wants marriage, too," added the insider.