The Insider.com

Rob Kardashian, 25, took to Twitter to seemingly call out his reported girlfriend (and presumably now ex) Rita Ora, 22, for cheating.

• December 03, 2012Adam Levine: F--- Honey Boo Boo's Parents
• December 02, 2012Chris Brown Back on Twitter, Shares RiRi Pic
• November 30, 2012What The...?! Best of the Week Awards
• November 30, 2012'Girls' Star Jemima Kirke Welcomes Baby
• November 30, 2012Five Things You Don't Know About Norman Reedus
• November 30, 2012Hot New Romance!

"She cheated on me with nearly 20 dudes while we were together, I wonder how many she will sleep with now that we apart? But I mean 20?!!!," he just tweeted. "How can a woman who is so busy trying to start her own career have time to be with so many dudes all while in a relationship?!"

Rob publicly confirmed they were dating after month of rumors in October, when he posted a kissing pic of the two together on Twitter. In August, he posted a photo of his and Rita's knuckles tattooed with each others' names. "Sh-t got crazy tonight… What can I say… #tatmynameonya," he tweeted.

Video: Rob Kardashian on His 'Glamorous' Life

He has since unfollowed Rita on Twitter and deleted all of his tweets and pictures on Instagram related to her.

The Sun is reporting that the two split due to the distance between them.

"It's really sad -- they really liked each other but with him living in L.A. and her over in London, it was becoming impossible to maintain a relationship," a source tells them.

Though the reported breakup now appears to be getting nasty.

"I'm actually disgusted a woman could give up her body to more than 20 dudes in less than a year's time while trying to start a career," he tweeted.

Related: Rob K Is Lying About Law School, USC Says

But as always, it appears his big sister Khloe has his back.

"Cheaters never prosper," she tweeted. "I'll be home today... Try and smile little brother."