"We wake up to all of these pictures of my brother getting engaged," Kim says in the clip for next Sunday's episode.
Even worse, it appeared Black Chyna's family was present when he proposed.
"He proposed in front of her whole family," Khloe says in the promo.
"How does our own brother not tell us?" Kim asks.
Back in April, Chyna posted photos of her wearing a gigantic 7-carat diamond ring along with the word "YES" three months after the couple began dating.
On Mother's Day, Rob Kardashian gushed about his lady love and their life ahead. "I fell in Love with her immediately because of how great of a mom she is and now I'm looking forward to starting a Family with her!" he wrote on Instagram.