In a preview for Keeping Up with the Kardashians, the family reveals how they knew nothing about Rob Kardashian's engagement until it was posted online

By Stephanie Petit
Updated June 13, 2016 11:00 AM
Gabe Ginsberg/Getty

Blac Chyna wasn’t the only one surprised when Rob Kardashian popped the question.

In a new preview for Sunday’s episode of Keeping Up with the Kardashians, Kim Kardashian, 35, reveals that Rob neglected to let his family know about his engagement plans.

It turns out the Kardashians found out about Rob’s engagement at the same time as everyone else through social media.

“We wake up to all of these pictures of my brother getting engaged,” Kim says in an interview, asking, “How does our own brother not tell us?”

It’s no secret that the Kardashians were initially not thrilled about Rob’s relationship with Blac Chyna, and they noticeably kept quiet after news of the engagement broke.

“No one [in his family] is jumping up and down with excitement today,” a source told PEOPLE of the Kardashian-Jenner clan at the time. “They have made a united decision as a family to not comment on social media yet about Rob’s engagement. The news is not shocking, and not totally unexpected.”

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Shortly after announcing their engagement, the couple also revealed that they are expecting a baby, the first child for Rob and second for Blac Chyna, who is mother to 3-year-old son King Cairo with ex Tyga.

Since filming, the family has started to come around and both Kim and Kylie Jenner, 18, have spent time hanging out with Blac Chyna and Rob.

Keeping Up with the Kardashians airs Sundays (9 p.m. ET) on E!