A new full-season supertease for Keeping Up with the Kardashians shows Khloé and big sisters Kim Kardashian West, 35, Kourtney Kardashian, 37, having it out with their baby brother over his then family-splitting relationship with Blac Chyna.
While the family is in Vail, Colorado, on a ski trip, the girls find out that the 29-year-old popped the question to his girlfriend of just a few months.
"He proposed in front of her whole family," says Khloé. "That's so f---ed up."
Once they've returned from their trip, the three sisters sit Rob down and lay into him – but he is not having it.
"Listen to the hostility in your voice," he tells one sibling. "It's exactly why I don't say anything. This is the first time I've ever proposed to someone in my life."
"Don't come at me with some bulls---." (Flash to the present: Khloé posted a Snapchat pic on Friday showing her holding hands with Rob.)
Also within the supertease, Kourtney struggles through relationship issues with ex Scott Disick (who is father to her three children), and tells her siblings (in front of Disick), that no successful relationship can happen in Los Angeles.
And Kim reveals that husband Kanye West wants more kids, but she fears her body can't handle another pregnancy.
The clip also gives a peek at Khloé's ex Lamar Odom's first meeting with Caitlyn Jenner and Kourtney's issues with Kylie Jenner's boyfriend, Tyga (whose ex is – you guessed it – Blac Chyna).
"I just want to call Tyga and go off on him," Kourtney tells Kylie, 18, after she finds out Disick had been partying with the rapper. The clip then jumps to Tyga, 26, having a sit-down with the eldest Kardashian where he explains that Scott needs to make his own decisions as a man.
Keeping Up with the Kardashians season 12 premieres Sunday at 9 p.m. ET on E!