Kim Kardashian is not about to be dethroned as the most popular celebrity in the entertainment world, and especially not by her stepparent, Caitlyn Jenner. There's a new rumor going around that Kim and Caitlyn are feuding big time behind the scenes, as the transgender star is stealing the Kardashian spotlight.

Caitlyn Jenner News 2015: Ex-Wife Kris Jenner Keeps Very Quiet During 'I Am Cait' Premiere

According to Hollywood Life on Monday, even though Kim and Caitlyn are trying to hide their feud from the public, they reportedly had quite a tense altercation off-camera recently. Kim is apparently upset that Caitlyn is using her ex-wife Kris Jenner to help promote her show while slamming her and their marriage to the media in the process.

A source told the site, "When Caitlyn started making derogatory comments about Kris in the Diane Sawyer interview and then in Vanity Fair, Kim felt as though she crossed the line. The fight on 'I Am Cait' paled in comparison to what Kim really said to Caitlyn."

Caitlyn Jenner News 2015: Reality Star Admits 'I Look Like Crap'

The insider added, "That confrontation for the show was basically a watered down recreation of how Kim really went after Cait. Caitlyn was refusing to talk to Kris, so Kim had to speak for her and she really let Caitlyn have it. Kim is happy for Caitlyn, but she is not going to let her diss Kris and hurt their family brand while promoting her own show."

So far, Kris herself has kept uncharacteristically quiet, as she hasn't mentioned Caitlyn or her new reality show on any of her social media accounts this past week.

Keep up with Enstars for all the latest news on Caitlyn Jenner and all of your favorite Kardashians.

Tags: caitlyn jenner Kim Kardashian