Academy Award-nominated actor Casey Affleck (To Die For, the Ocean's Eleven films, The Assassination of Jesse James by the Coward Robert Ford) is the younger brother of Oscar winner Ben Affleck (Armageddon, 2010's The Town), with whom he appeared in Chasing Amy (1997) and Good Will Hunting (1997). Casey starred in 2007's critically acclaimed Gone Baby Gone, written and directed by his brother. He is married to Summer Phoenix (younger sister of Joaquin and River Phoenix). He made a cameo in the Joaquin Phoenix-directed video "Tired of Being Sorry" for Balthazar Getty's band Ringside. Casey and Summer also appeared together in 2000's Committed.
In 2010, Casey made his directorial debut with the mockumentary I'm Still Here, which starred his brother-in-law Joaquin. The film chronicled Joaquin's faux decision to leave the acting world and become a rapper.
Interestingly, in 2012, the New England Genealogical Society announced that Ben and Casey are distant cousins of good friend (and Ben's Good Will Hunting co-star/co-writer) Matt Damon. Casey and Matt starred together in 2002's Gerry. They are tenth cousins, once removed. Other distant relatives reportedly include President Barack Obama and the late Princess Diana.