Olivia Newton-John is putting family first. The Australian singer and actress, 64, has postponed a Las Vegas concert series in order to support older sister Rona Newton-John, who was recently diagnosed with brain cancer.

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Sharing "the very sad news" with Entertainment Tonight, the Grease star explained, "I have decided to postpone my forthcoming Las Vegas residency to spend time with her and our family." Olivia herself battled (and defeated) breast cancer 20 years ago, and adds: "As a cancer 'thriver' myself, as many people are, I am very aware of the importance of love, support and family during this journey she is about to begin."

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The "Physical" singer had been preparing to perform multiple shows at the Flamingo Casino during Donny and Marie Osmond's break. "I want to thank everyone in advance for respecting our privacy during this difficult time," adds the star, who is expected to reschedule her Vegas dates at a later time.

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Like her sister, Rona Newton-John is also an actress, and was married to her sister's late Grease costar Jeff Conaway from 1980 to 1985. She and Conaway shared son, race-car driver Emerson.


This article originally appeared on Usmagazine.com: Olivia Newton-John's Sister Has Brain Cancer, Singer Delays Vegas Shows