"We have lost Monty Brinson after a brave battle with cancer," he wrote next to a photo. "His heart was as big as the moon and he was loved by all he met. He will be sorely missed. I love you always!"
"Heartbroken to hear the sad news of my Uncle @MontyBrinson's passing after his long brave battle with cancer," she wrote in a caption. "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."
In his final days, Brinson had been keeping the public updated via Instagram on his health condition and outlook on life.
Last week he wrote, "Today is a great day for me as I do wish for everybody to be surrounded by angels all morning, afternoon and evening. Ever since I was diagnosed with cancer ... the few setbacks along the way have been encouraging and inspiring. What's made me is the love and kindness from around the world that ... I have touched. I hope there is enough time left in me to write my experience with love kindness."
Friday was the last day Brinson posted a message to his followers. "May the positive energy of the universe surround you, flow through you, bring to you peace to your mind, love to your heart," he wrote.
Richards, 51, and Brinson were married from 1985 to 1988 and have one daughter together, 29-year-old Brooke.