Kylie Jenner questioned if Tristan Thompson was 'the worst person on the planet' after he admitted to cheating on Khloé Kardashian on his 30th birthday

• Episode nine of "The Kardashians" showed the sisters' reactions to Tristan Thompson cheating on Khloé.
• News broke in December 2021 that Thompson had cheated on Kardashian on his birthday in 2021.

After news broke that Tristan Thompson had cheated on Khloé Kardashian on his 30th birthday, Kardashian's younger sister Kylie Jenner asked if he was the "worst person on the planet."

In the ninth episode of "The Kardashians," Kim Kardashian was working out early in the morning when she learned that Thompson had cheated on her sister, which he said in court documents responding to fitness instructor Maralee Nichols' claim that he had fathered her child.

When she reached her sister, Kylie Jenner, she said that Kim had to have been "lying."

"Is Tristan like the worst person on the planet?" Jenner asked Kim over the phone.

E! News reported on December 3, 2021, that Thompson said in legal filings that he had sex with Nichols on his birthday in March 2021, when he and Kardashian were dating. Thompson requested a paternity test after Nichols filed a lawsuit against him in June requesting that he pay "reasonable expenses of pregnancy and birth," E! News reported. Thompson later announced in January that a paternity test had confirmed him to be the father of Nichols' child.

In the court documents, per E! News, and which Kim excerpted on the show and during the phone call with her sisters, Thompson said that he remembered having "sexual intercourse" with Nichols in March "because it was my birthday."

A post shared by Khloé Kardashian (@khloekardashian)

Thompson and Kardashian have been in an on-again, off-again relationship since 2016, and share a daughter, True Thompson. Kardashian said on an episode of the family's Hulu series that she and Thompson got back together in late 2021. In an April ABC News interview, however, she said that Thompson was "just not the guy" for her, confirming that their relationship had ended since filming.

"She doesn't deserve this. This has to be her final sign," Jenner said on the phone call. "Like, this is insane."

At the end of the episode, Kardashian calls him back, prompting her to end the call with Kourtney and Jenner.

"What the fuck is this?" Kardashian asks Kim when she sees what she sent.

Danielle King, the showrunner of "The Kardashians," previously told Insider that the crew was at Kim's house to film something completely different when Kim saw the headlines about Tristan. At the time, she told Insider that her heart was "utterly breaking" for Kardashian.