Karen Houghton, sister of reality TV star Kris Jenner, has died suddenly.“It is with the heaviest heart and deepest sadness that I share that my sister Karen passed away yesterday unexpectedly,” Jenner wrote in a post on Instagram on Tuesday.“My heart aches for my mom MJ and my niece Natalie and I pray that God guides us all through this difficult time.”Houghton was not involved in the Kardashian-Jenner reality TV juggernaut that catapulted Kris and her family to global superstardom.The two sisters had a rocky relationship, with Houghton alleging in a 2013 interview that Jenner had changed after becoming famous, but Jenner remembered her sibling fondly in the post.“Karen was beautiful inside and out. She was the sweetest, kindest, the most sensitive and vulnerable and so so funny,” she wrote.“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,” continued the tribute.“We must tell those we cherish how much we love them. I love you my beautiful sister.”Jenner’s tribute drew reactions from celebrities such as James Charles and Zoe Saldana.“So so so sorry for your loss mama 💔,” wrote Charles, while Saldana responded: “Our hearts are with you. So sorry lady.”