The Kardashian clan is reportedly not happy with Khloé’s baby daddy Tristan Thompson—least of all, little brother Rob. According to People magazine, Rob is “furious” at Thompson over rumors that the 27-year-old has been cheating on Khloé throughout her pregnancy.

“Khloé has always been there for Rob and he hates that she was hurt—he knows what it feels like to be screwed over by someone you trusted,” a source told the magazine. “Rob won’t forgive Tristan for this.”

Rumors that Thompson was cheating on Khloé broke last week, when footage surfaced of the Cavs player canoodling with another woman on a rooftop bar in Manhattan the weekend before the 34-year-old reality star gave birth to their first daughter. Following that bombshell, The Shade Room posted photos of Thompson going up to his hotel room with the other woman that same weekend, and TMZ published video of Thompson making out with two women back in October. He reportedly may have cheated on Khloé with at least five different women.

A source also told People on Tuesday that Kim Kardashian West and Kanye are also frustrated with the NBA star. “They both feel Khloé has gone through so much and that she deserves being happy. They can’t believe that Tristan has been going behind everyone’s back. They find his behavior disgusting,” the source said. “Kim is very protective of Khloé and is especially upset. She can’t imagine Khloé will stay with Tristan, but will support her sister either way.”

So far it seems that Khloé is attempting to keep the peace with Thompson for the sake of her first child True, who has Thompson’s last name. “Khloé still very much loves Tristan, and this baby is one half his,” a source told People. “True is their child together. Giving the baby his last name was never in question.”

Meanwhile several celebrities, including Amber Rose and Cardi B, have offered Khloé condolences and advice amid the scandal.

Khloé welcomed her baby girl Thursday morning in Ohio, where she and Tristan are currently staying, though she plans to return to LA “very soon.”