Zac Efron says his younger brother keeps him grounded

Los Angeles - Zac Efron relies on his younger brother for support.

The 25-year-old actor - who completed a stint in rehab earlier this year for alleged cocaine and alcohol abuse - shares a strong bond with his sibling, Dylan, and often turns to the 21-year-old for advice and support when having a tough time.

He said: "My family's my rock. I know that they're not going anywhere. More and more I rely on my little brother to keep me grounded. He's 21 now."

The Parkland star also believes it's important to surround yourself with good friends and says his pals are there for him when he can't turn to his family.

He added: "I know my family's always going to be there, and then there's also some times when life changes, they can't always be there for you in the way that you need, so I rely on my friends."

The hunky star was speaking at a Q&A event to promote his new movie That Awkward Moment, which sees him appear naked, and Zac admits he experienced an embarrassing moment of his own on set when a modesty pouch failed to properly cover his genitals.

Quizzed about his most awkward moment on set, he said: "For sure getting naked on the toilet ... There was, like, a sock thing and it fell off. You just have to cup your hands!"