Joan Collins Posts Tribute to 'Brave Baby Sister' Jackie on Twitter

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There's nothing quite as special as a bond between sisters.

Joan Collins took to Twitter to share a photo tribute to her sister, Jackie Collins, who passed away from a long, private battle with breast cancer on Saturday. The best-selling author was 77.

NEWS: Jackie Collins Dies of Breast Cancer at 77

"Farewell to my beautiful brave baby sister," Joan tweeted with a photo of the two as children. "I will love you and miss you forever. Rest in peace."

Just days before Jackie's passing, Joan retweeted a fan's sweet photo of the siblings.

"You could search the whole planet and not find two sister[s] who are as beautiful as @Joancollinsdbe and @jackiejcollins," the tweet read.

Other stars
, like Keeping Up With the Kardashian's Kris Jenner, took to social media to pay tribute.

"I'm so sad to hear about the passing of Jackie love and prayers go out to her family and friends and to her sister Joan," she wrote. "What an amazing woman.... It was a joy and honor to have known her."

Jackie was diagnosed with stage 4 breast cancer over six years ago, but she chose to keep her illness as private as possible.

Collins was a true legendary author. She wrote a total of 32 books, all which landed on The New York Times bestsellers list. In addition to Joan, Collins is survived by her three daughters, Tracy, Tiffany, and Rory, and her younger brother, Bill.

PHOTOS: 6 Reasons Why Jackie Collins Reigned Supreme

"It is with tremendous sadness that we announce the death of our beautiful, dynamic and one of a kind mother, Jackie Collins, who died of breast cancer today," the Collins family confirmed to ET Saturday in a statement. "She lived a wonderfully full life and was adored by her family, friends and the millions of readers who she has been entertaining for over 4 decades."

Private services will be held for her family in both the United States and the United Kingdom. They ask that in lieu of flowers, donations be sent to the Susan G. Komen Breast Cancer Organization and Penny Brohn Cancer Care, respectively.

Watch more about Collins' life and prolific career in the video below: