Rick Hilton, the husband of Kim's sister Kathy Hilton, posted a touching Instagram message announcing Monty's death on Sunday, January 24. "We have lost Monty Brinson after a brave battle with cancer. His heart was [as] big as the moon and he was loved by all he Met," Rick wrote. "He will be sorely missed. I love You always!"
Kim and Monty were married from 1985 to 1988. They have one daughter together, Brooke, now 29 years old, who was married last May.
Since their divorce in 1988, Kim and Monty have remained close with the RHOBH mom taking care of her ex-husband throughout his battle with lung cancer.
Shortly before Monty's death, Kim took to Twitter to thank her fans for their support during this difficult time. "Hi Everyone...I've missed U all," Kim tweeted on January 22. "Thank you for all the Love and Prayers for Monty! Your messages touch my heart."
Monty also stood by Kim during her time in rehab and arrests last year. "One day the people that didn't believe in you will tell everyone how they met you. That quote is in honor of @kimrichards11 all I will say at this time besides being best friends, and personally a person who has a great heart is thankful to all her fans and friends for believing in her," he wrote in the caption to a throwback photo of the couple posted on Instagram last year. "Without going into detail 90 per-cent of what you read is completely false. But for her fans that have stayed with her through this roller coaster will see her very soon at what she's done best all her life since the age of 4. I'm excited for her. And personally I would like to thank everyone who stood by her through this rough time. Remember everyone in life goes through a rough time one way or another. I always say know the facts before being judgmental."
With his many inspirational Instagram posts, it looks like Monty was a fighter right up until the end. "I'd I'd like to thank all the the people who have crossed my path," Monty wrote in one of his final Instagram posts. "You've all touched my heart may everyone have a blessed night and much love to everyone."
UPDATE: Kim's niece Paris Hilton also shared her condolences on Instagram Monday. "Heartbroken to hear the sad news of my Uncle @MontyBrinson's passing after his long brave battle with cancer," Paris wrote. "He was such an incredible man with such a huge heart. He was so insightful & positive about life, even with all he was going through. He always had a smile on his face & lit up the room with his positive energy & fun personality. He will be truly missed. My thoughts & prayers are with @BrookeWiederhorn @KimRichards11 & his family. #RIPMontyBrinson."
Kim's sister Kyle Richards has also showed her love for Monty on Instagram Monday. "We love you @montybrinson you will be missed dearly," Kyle wrote in a post that featured several pics of her former brother-in-law throughout the years. "The kindest, gentlest soul who inspired so many with his positive attitude throughout his battle with cancer. May you rest in peace now."
See photos of Kim throughout the years, below.