Like real-life stepbrothers (only infinitely funnier and better paid), Will Ferrell and "SNL"-alum writer Adam McKay have a familiar comedic bond, cranking out smartly dopey screenplays about self-absorbed man-boys every few years (Anchorman, Talladega Nights). In this outing, Brennan Huff (Ferrell) and Dale Doback (John C. Reilly) are two adult doofuses still languishing in their respective single-parent nests. Those nests collide when Mr. Doback and Ms. Huff get hitched and make house, forcing the deadbeat sons into an uncomfortable new brotherhood. There's the inevitable dramatic rift that rips the elder lovers apart, and the subsequent scheming their progeny hatches to bring them back together--but the humor's sincere and unexpected. 98 minutes R.