Their film noir tale mirrors the real-life Bulger brothers of South Boston ; William Bulger became a state senator and president of the University of Massachusetts , while James Bulger , better known as Whitey , became a mobster and a fugitive from the F.B.I . But viewers are more likely to see the Caffees as the unKennedys , a cautionary tableau of what that Massachusetts dynasty might have been like if its patriarch , Joseph Kennedy , had not made a fortune as a bootlegger during Prohibition . ''