Ashlee Simpson and Pete Wentz know when to put their differences aside.
The exes, who finalized their divorce a year ago, reunited yesterday (Nov. 20) to celebrate their son Bronx's 4th birthday. Alongside Wentz, 33, and his 24-year-old model girlfriend Meagan Camper, Simpson, 28, helped set up the superhero-themed party at The Coop in Studio City, Calif.
The trio "were at ease in each other's company," according to the Daily Mail and seemed to be having a great time as they welcomed party guests, including Nicole Richie and her daughter Harlow and Simpson's parents, Tina and Joe, who arrived separately after announcing their divorce.
Not spotted at the bash were Jessica Simpson, her daughter Maxwell and fiance Eric Johnson. Plus Simpson's boyfriend, "Boardwalk Empire" star Vincent Piazza, was nowhere to be found.
Check out pictures of Ashlee, Pete and Bronx at the party below: