Olivia Newton-John broke the news about her sister's death through a post on her Facebook page.
“She was surrounded by the love of her four children-Fiona, Brett, Tottie and Emerson and her wonderful friends,” Newton-John wrote on her Facebook page. “I will miss her forever-my beautiful, smart, talented, funny, brave sister Rona.”
Last month, the "Grease" actress announced she'd be putting her plans to move to Las Vegas, Nevada on hold to take care of her sister.
Olivia Newton-John is a cancer survivor herself.The 64-year-old actress was diagnosed with breast cancer almost 20 years ago. She has been free of the disease after getting a mastectomy and undergoing treatment.
Rona Newton-John, who was also an actress, had been working on a memoir "The Dark Side of Charisma" over the past years, ABC news reported. The book is set for release this summer.
The Newton-John family has requested that in lieu of flowers people send donations to the Olivia Newton-John Cancer & Wellness Center, where a brain tumor wellness program will be started in Rona's name.