On Sunday, Zac Efron took to Instagram to share a beautiful message about his late cousin in honor of both of their birthdays. Zac, who turned 28 on Oct. 18, posted a flashback photo from their childhood, writing, "Happy birthday to my cousin and best friend, Emily, who passed away from cancer 2 years ago - she was 28 like me. 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." See Zac's post above, and in celebration of his big day, check out his sexiest shirtless moments [2] in GIFs!