Kris Jenner took to Instagram to announce "with the heaviest heart and deepest sadness" that her sister, Karen Houghton, passed away on March 18 aged 65.
The 68-year-old mom-of-six shared a number of unseen photos of the two together over the years, including snaps with their mom Mary Jo Campbell, a young Kourtney Kardashian, and the late Robert Kardashian.
Kris penned an emotional tribute to her sister: "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."
She added: "Karen was beautiful inside and out. She was the sweetest, kindest, the most sensitive and vulnerable and so so funny. 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. Karen’s passing is a reminder that life is so short and precious and tomorrow is never promised. We must tell those we cherish how much we love them."
To sign off the heartbreaking announcement, she added: "I love you my beautiful sister."
Not much is known about Karen, who has lived a life relatively outside of the spotlight. According to reports, she is a part-time nerse who has authored two cookbooks; her first, Naturally Gourmey, came out in 2010 while the second volume was released in 2013. She is succeeded by her daughter Natalie, who is estimated to be in her mid-20s.
While Kris didn't often speak about her relationship with her sister, in her 2011 autobiography she explained: "We loved each other, and we were there for each other through thick and thin, and to this day, we are a part of each other's lives."
TMZ reported that the cause of death is currently unknown, with county officials attributing her death to natural causes for now.