"When you point the camera at him he just makes your movie better," says Ben Affleck of his little brother Casey, who's stepped out of his sibling's shadow by landing an Oscar nod and becoming one of Hollywood's most respected actors.
While he saw his big brother soar to fame with blockbuster after blockbuster, Casey chose a different path. He steadily built his reputation with an eclectic range of roles, earning an Oscar nomination in 2008 after 12 years in the business.
Born on August 12 1975, in Falmouth, Massachusetts, Casey was raised in Cambridge, along with Ben, by his mother Chris, a teacher. His father Tim, a some-time actor who also worked as a mechanic and janitor, left the family when the boys were still young. As kids the brothers both worked as extras in TV ads, leading to Casey making his first significant small screen appearance in 1988's Lemon Sky. He followed this up two years later playing a teenage Bobby Kennedy in the miniseries The Kennedys Of Massachusetts.
Like Ben and their childhood buddy Matt Damon, Casey was inspired by his school's acting teacher, Gerry Speca. "I was lucky," he says. "I had a teacher who encouraged me. Anybody who walked into his class wanted to be an actor, he just turned them on to the beauty of it. I owe him everything."
After leaving high school he headed for LA and considered going on to college, but his plans were interrupted when he was cast as a troublesome teen in 1995's To Die For. On the set he became good pals with co-star Joaquin Phoenix, through whom he would meet his future wife, Joaquin's sister Summer Phoenix.
Filming completed, he went on to study at George Washington University before transferring to New York's Columbia University. He was two years into a physics and astronomy degree before being coaxed back onto the big screen by the role of smart-mouthed Morgan, the onscreen brother to real-life sibling Ben in 1997's Good Will Hunting, written by Ben and Matt Damon. The same year the brothers also shared the screen in comedy Chasing Amy, with Casey in a cameo role.
While Good Will Hunting sent Ben's career stellar Casey focused on strong character roles in independent productions. He appeared opposite Kate Hudson in 1998 movie Desert Blue and the following year in comedy 200 Cigarettes, which again featured Ben. In 2001 and 2001, while his brother hit the big time, Casey admitted making two movies he wasn't too proud of - black comedy Drowning Mona and horror flick Soul Survivors. His cameo appearance in the lacklustre sequel to American Pie didn't help either.
Things started to look up, however, when he was recruited to join the A-list cast of heist caper Ocean's Eleven alongside Matt, Brad Pitt and George Clooney. And the hit franchise' subsequent sequels helped raise his profile further. Like Ben, he collaborated on a script with Matt, resulting in 2002's Gerry, in which he also starred. The same year he and Summer, whom he had started dating in 2001, went with Matt to London to appear in the West End production of This Is Our Youth.
He and Summer who describes the actor as "the most generous guy I have ever met" - became engaged at the end of 2003. They welcomed their first child, son Indiana August, the following May in Amsterdam, where Casey was shooting Ocean's Twelve. They married on June 3, 2006, and gave Indiana a brother in January 2008.
Both lifetime vegans, they are actively involved in animal rights.
In 2005 Casey finally came into his own as a leading man, earning critical plaudits for his title role in Lonesome Jim and following it up with Last Kiss. But it was 2007 that saw him became a bona fide star after he turned in a series of mesmerising performances. As well as returning in Ocean's Thirteen he was cast as wannabe outlaw Robert Ford opposite Brad Pitt in The Assassination Of Jesse James By The Coward Robert Ford.
While the movie didn't live up to expectations at the box office, Casey was feted for his performance as the man who befriended the train robber then betrayed him to the authorities before shooting him in the back. The role earned him an Oscar nod for best supporting actor plus a clutch of prestigious awards, including Screen Actors Guild and Critics' Choice trophies.
Also cementing his reputation as a leading man was his big brother's 2007 directorial debut Gone Baby Gone. Casey starred as a private investigator hunting for an abducted four-year-old girl Boston. "The brothers Affleck both emerge triumphant in this mesmerizing thriller," enthused Rolling Stone magazine at the time.