The Hills and Laguna Beach star posted an emotional message to Instagram following the tragic news that Michael Cavallari's body had been discovered in Utah nearly two weeks after he went missing.
Kristin, 28, said: "My heart is in a million pieces. Mikey, I could always count on you to make me laugh. You had such a good heart and will be forever missed. I'm at a loss for words but I know u are in a better place and finally at peace. I love u so much RIP."
She accompanied her post with a photo of them as children.
A statement issued to People magazine said: "We want to thank everyone for their love, support and prayers during this very difficult time. We have just been informed by the authorities my brother's body has been found. This is a very painful time and we are still processing it all. We kindly ask everyone please respect our privacy during our time of grieving."
Concerns were raised about Michael's wellbeing when his car was found abandoned on a road in Utah with the engine still running. His mobile phone and laptop were still inside.
A statement released to ABC7 Chicago by the Grand County Sherriff's Office said: "At approximately 10:30 a.m. search crews located remains believed to be that of Michael Cavallari. At this time, the body is being transported to the Office of the Utah Medical Examiner for positive identification and to determine the cause of death.
"The search crews were searching the Salt Wash area, near exit 175 on I-70 in Grand County. The terrain where the body was located is a steep and very rocky area."
Michael was last seen California on 25 November. His car was found abandoned on 27 November with no sign of him anywhere nearby. CCTV footage showed he'd visited a convenience store in Utah earlier that day.
It's alleged that Michael was arrested and bailed a few days before his disappearance after a woman accused him of holding a gun outside her home while they argued. He had denied doing anything to the woman.