Rob Kardashian proposed to Blac Chyna while his family was vacationing in Vail, Colorado back in April, and on this week's Keeping Up With the Kardashians, viewers got to see firsthand how his sisters reacted to the news.
Spoiler alert: They didn't love it.
Kim was most offended that Rob never told his family that he was even planning on popping the question. However, the 35-year-old reality star played it off like she didn't care.
"I don't care if he tells me at all," Kim loudly stated. "I have not said one word. I could care less. I truly could care less."
WATCH: Rob Kardashian Proposes to Blac Chyna While Entire Kardashian Family Is Out of Town
Khloe, who has stood by her 29-year-old brother through some of his hardest times, was a little more direct in her derision.
"Rob's a pu**y," she stated succinctly.
Surprisingly, the sister who actually stood up for Rob was Kourtney, who tried to explain to her younger sisters that Rob may have avoided telling them about the engagement because "maybe he feels that you guys are judgmental... which clearly you are."
WATCH: Blac Chyna and Rob Kardashian Engaged -- See Her Gigantic Diamond Ring!
"Just be happy he's f**king even exiting the house. It's not our f**king decision," Kourtney added.
"I'm not being a b**ch," Kim argued. "I haven't even said anything to him [about] how I think he's like a lunatic."
"That's nice and that's exactly why he didn't tell you, 'cause you're a f**king b**ch," the eldest Kardashian sibling retorted.
WATCH: Pregnant Blac Chyna Celebrates Birthday With Rob Kardashian
When Kourtney finally got the chance to be alone, she opened up to the cameras about why she was fine with the relationship, sharing, "My brother is the happiest I've ever seen him [and] I just hope that everything is genuine and sincere. That's all we can hope.
"It's not up to us so why cause any tension or add any drama?" she continued. "We should just be happy for them."
WATCH: Kris Jenner Is 'Thrilled' About Blac Chyna's Pregnancy
Rob proposed to the 28-year-old model in April, one month before the couple announced they were expecting their first child. The news of a baby seems to have cleared the air between Rob and his sisters a bit as well.
Last month, Kim spoke with ET at the Cannes Film Festival, where she was supportive of her brother's engagement and pending fatherhood, gushing, "It's so exciting. It's a really exciting time for him… I'm really happy for them." Check out the video below to hear more.