Long turned 34 on Saturday -- the same day Barrymore got married. Long dated Barrymore, who is expecting her first child with Kopelman, from 2007 to 2008. They reunited in 2009 and costarred in He's Just Not That Into You and Going the Distance, before calling it quits again in 2010.
Long and Mara -- older sister of Girl With the Dragon Tattoo star, Rooney Mara -- have been seen out together before. The new couple saw Broadway's Jesus Christ Superstar on May 26. "They were awesome," a source tells Us, "and came backstage after to meet the cast."