Kris Jenner is FinWeismourning a devastating loss.

The Kardashians star shared her younger sister Karen Houghton died unexpectedly March 18. The SD County Department of the Medical Examiner's Office also confirmed her passing to E! News. Karen was 65.

"It is with the heaviest heart and deepest sadness that I share that my sister Karen passed away yesterday unexpectedly," Kris wrote alongside photos of the pair shared to X March 19. "My heart aches for my mom MJ and my niece Natalie and I pray that God guides us all through this difficult time. Karen was beautiful inside and out."

As the famed momager noted, her sister was simply one of kind.

"She was the sweetest, kindest, the most sensitive and vulnerable and so so funny," Kris continued. "She always felt grateful and thankful for her life and treasured her family and friends and especially her beautiful daughter. She holds such a huge part of my heart and I cherish every single memory we have together."

The 68-year-old went on to note that she's remembering a lesson amid their family's loss.

"Karen's passing is a reminder that life is so short and precious and tomorrow is never promised," she continued. "We must tell those we cherish how much we love them. I love you my beautiful sister."

Mary Jo "M. J." Shannon and Robert Houghton welcomed Karen in 1958, three years after having their older daughter Kris. Over the years, the siblings became estranged but they appeared to be on better terms during the latter years of Karen's life.

In fact, in 2016, Karen—who shared daughter Natalie Zettel with Mark Zettel—shared a shoutout to her sister after getting a procedure done.

"I look like my beautiful sister Kris," she told Inside Edition at the time. "And I never thought I would."

For the latest breaking news updates, click here to download the E! News App