1. Zachary David Alexander Efron, 31, is an actor. 2. He is known for his roles in "High School Musical," "Neighbors" and "The Greatest Showman." 3. Efron has said he was a class clown growing up. 4. His estimated net worth as of 2015 was $18 million. 5. He has struggled with alcoholism and substance abuse.

Social media is going nuts over Zac Efron's photo with his younger brother Dylan Efron

People love Zac Efron so much that they've even started to creepily fall in love with his upcoming role as serial killer Ted Bundy – so when the actor posted a shirtless photo with his brother, you can probably guess the intense reaction.

The photo, which Efron posted for his younger brother Dylan's birthday, shows both men showing off their abs at the base of a picturesque waterfall.

"Happy birthday @dylanefron! Honestly, I never in my wildest dreams, would’ve thought that the little terror, devil, monster that was my little brother would turn into my very best friend," Efron wrote. "I’m so proud of the man you are today. Let’s save the world together- one waterfall at a time. Love ya little brother!"

Here are some of the best reactions on Twitter:

» Zac Efron channels serial killer Ted Bundy in 'Extremely Wicked, Shockingly Evil and Vile' trailer

"Zac Efron has a hot, younger brother I REPEAT, ZAC EFRON HAS A HOT YOUNGER BROTHER," one user tweeted.

"Someone should probably tell Zac Efron not to thirst trap with his brother...," another tweeted. "...but it’s not going to be me."

"That pic of zac efron with his brother has got me so thirsty. Help me," another said.

"So we all know that Zac Efron is a major hottie, but have you seen his brother Dylan!!!! Cuz danggggggg!!" another tweeted with heart-eye emojis.

"Unpopular opinion: Zac Efron’s brother is hotter than Zac Efron," another said.

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