See the Kardashians Learn That Rob Got Engaged to Blac Chyna on 'KUWTK': 'How Does Our Own Brother Not Tell Us

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Ouch! Being related to Rob Kardashian did not give Kim, Khloe, or Kourtney Kardashian any insider info into his engagement to Blac Chyna. The sole male Kardashian kept his family in the dark when he popped the question to his pregnant fiancée back in early April.

The ladies were on a family vacation when they learned of the news, and the moment was captured on the family’s reality series.

WATCH: EXCLUSIVE: Ryan Seacrest Talks 'Compelling' Rob Kardashian-Blac Chyna Reality Show: 'They’re in a Happy Place'

“We wake up to all of these pictures of my brother getting engaged,” Kim says in the preview clip for next week’s episode of Keeping Up With the Kardashians.

In the clip, Khloe is reading articles online about her brother’s engagement, saying, “He proposed in front of her whole family.”

Rob’s sisters look shocked as they continue to see more news about the engagement.

WATCH: EXCLUSIVE: Blac Chyna Talks Wedding Planning With Rob Kardashian: 'We're Taking Things Slow'

“How does our own brother not tell us?” Kim asks in her side interview.

Since the news of their engagement broke, Rob and Chyna have also revealed that they are expecting a child together and will have their own six-episode spin-off reality series, Rob & Chyna.

Keeping Up With the Kardashians airs Sundays at 9 p.m. ET on E!

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