The Kardashians React to Being Blindsided by Rob's Engagement to Blac Chyna on 'KUWTK': 'Why Would We Congratu

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Rob Kardashian's quickie engagement to Blac Chyna was far from a happy occasion for the Kardashian clan.

In a preview for Sunday's episode of Keeping Up With the Kardashians, Rob's sisters -- Kim, Khloe and Kourtney Kardashian, as well as Kylie Jenner -- react to the news from April that Rob popped the question to Blac Chyna while his entire family was away on vacation in Vail, Colorado.

As Kim reads aloud a report that the family was "blindsided" by the big news, the sisters couldn't look less excited while getting their hair and makeup done.

WATCH: EXCLUSIVE: Blac Chyna Says She Thinks Rob Kardashian Will Be an 'Overprotective' Dad

"Why would we congratulate him?" Khloe says bluntly, referring to the article taking note of the fact that nobody in the Kardashian family acknowledged Rob and Chyna's engagement on social media following the news. "And no one should congratulate them. That's so desperate and fake of whoever does first 'cause I know someone's gonna break."

Kylie then comments that her now-ex Tyga -- who shares a 3-year-old son, King Cairo, with Chyna -- tweeted that "everyone deserves to be happy." The 18-year-old reality star continues to stress that she could care less about all the drama.

"People are trying to make it this big feud, it just ... it is what it is, we just want Rob to be happy," she says.

"I just feel like the world thinks that we care so much and they're making it this huge big deal, when in reality none of us really care," Kylie later tells the cameras. "We just want Rob to be able to tell us when he's gonna do something so big like this."

Meanwhile, the siblings' mother, Kris Jenner, admitted to KUWTK cameras to being "in shock" that her 29-year-old son popped the question.

"I wake up to a gazillion text messages, which is never good news," she explains. "And I'm reading through them and realize Rob got engaged last night, he got engaged! And it's sorta coming out of left field. I think I'm just in shock."

"To hear that Rob got engaged through social media is a bit disappointing to say the least," the momager added. "He should've told me first, or even talked to the family about it or mentioned it to his sisters, but I had no idea."

WATCH: Kim and Khloe Kardashian Visit Rob's New House, Mock His Decorations

Not surprisingly, Kim -- who has a history of butting heads with Rob -- appears the least bothered by the big news ... or at least claims to be.

"I don't care if he tells me at all," Kim loudly stated in a previous KUWTK episode. "I have not said one word. I could care less. I truly could care less."

Watch below: