Los Angeles, California - The Kardashians star Kris Jenner has revealed that her younger sister, Karen Houghton, tragically passed away on Monday.

On Tuesday, the 68-year-old Kardashian-Jenner matriarch announced the unexpected passing of her sister and the aunt of her kids, Kim Kardashian, Kourtney Kardashian, Khloé Kardashian, Rob Kardashian, Kylie Jenner, and Kendall Jenner.

Under the Instagram post that featured throwback pics of the siblings, Kris wrote, "It is with the heaviest heart and deepest sadness that I share that my sister Karen passed away yesterday unexpectedly."

"My heart aches for my mom MJ and my niece Natalie and I pray that God guides us all through this difficult time."

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The famous momager shared that her late sister was "beautiful inside and out" and was the "sweetest, kindest, the most sensitive and vulnerable and so so funny."

Kris concluded that Karen's passing is a "reminder" that "life is so short, adding, "We must tell those we cherish how much we love them. I love you my beautiful sister."

The Kardashians season 5 will premiere on May 23.