Josephine Cusumano
Dec 19, 2015 @ 6:30 am

One of Hollywood's most eligible bachelors is turning 37 today! That lucky man is Jake Gyllenhaal, famously known for his role in Brokeback Mountain and his amazing transformation in Southpaw.

Fans got to see a whole new side of the actor (and his abs) when he portrayed a heavyweight boxing champ. He completely transformed his body for the role—and it wasn't without a lot of hard work. The actor revealed to People that his workout routine included 1,000 sit ups, 100 pull-ups, 100 dips, 200 squats, jumping rope, and running eight miles a day.

Steve Granitz/WireImage

Aside from his method acting, Gyllenhaal also appeared in countless films and was even nominated for two Golden Globes for his respective roles in 2010's Love & Other Drugs and 2014's Nightcrawler. He even earned an Oscar nod for his performance in 2005's Brokeback Mountain opposite the late Heath Ledger.

RELATED: Jake Gyllenhaal Reminisces About Heath Ledger

When Gyllenhaal isn't impressing the critics with his onscreen work, he's shocking his older sister, Maggie Gyllenhaal, who couldn't believe the transformation he underwent for Southpaw. "He's always really into physical transformations for his work," she dished to InStyle, adding, "I'm always curious about his way in, because it's so different than mine. It's kind of amazing, and it's sort of interesting to watch."

In honor of Gyllenhaal's big day and his special bond with sister Maggie, look back at some of Hollywood's famous siblings—including the Gyllenhaals!

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