Zac Efron Posts Touching Birthday Tribute to His Cousin Who Died of Cancer

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Zac Efron wasn't just thinking about himself on his 28th birthday this past Sunday.

The Neighbors 2 star took to Instagram to also remember his late cousin Emily, who died of cancer two years ago. The close relatives shared the same birthday.

"Happy birthday to my cousin and best friend, Emily, who passed away from cancer 2 years ago -- she was 28 like me," Zac Instagrammed alongside a childhood photo of the two at the beach. "We share the same birthday and this day is forever ours. My birthday wish is for you to donate anything you can to @su2c. The link is in my bio. Thank you everyone for all the birthday wishes. Love you."

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Efron has been a longtime supporter of Stand Up To Cancer (SU2C), which raises funds for groundbreaking new research. In 2010, the heartthrob appeared in a PSA for the organization alongside stars like Kristen Bell, Dakota Fanning, Andrew Garfield, and Olivia Munn.

WATCH: Eva Mendes Jokes She's Too Tired From Her Baby to Read a Teleprompter at Stand Up To Cancer Event

In August, Efron's ex, Vanessa Hudgens, sadly revealed that her father, Greg Hudgens, has stage four cancer. The 26-year-old actress broke the news when she accepted an award for Breakthrough Performer at the 2015 Industry Dance Awards in Los Angeles -- an event that benefits The Circle of Hope, a charity for dancers who have survived cancer -- and also dedicated the award to her boyfriend Austin Butler's mother Lori, who died of cancer last year.

Watch Hudgens' emotional speech below:

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