"Yesterday I said goodbye to best the friend I've ever had in my life," Richards wrote in the heartfelt caption. "Monty was an amazing person with an amazing soul ... We shared over 30 years of Love & Happiness and brought a beautiful daughter into world. I am so grateful for all that we shared."
"I love you Monty, my angel in heaven," the 51-year-old reality star concluded. "I know that we be together again one day. I will carry you in my heart always my love ... until then, may you rest in peace."
Brinson died Sunday at 58 after a long battle with lung cancer. A source close to Brinson confirmed to ET that he passed away in a medical facility surrounded by his family.
Richards and Brinson tied the knot in 1985 and remained together for three years until divorcing in 1988. The couple welcomed their daughter, Brooke, in 1986.