Brennan Huff (Will Ferrell) is a sporadically employed 39-year-old who lives with his mother, Nancy (Mary Steenburgen). Dale Doback (John C. Reilly) is a terminally unemployed 40-year-old who lives with his father, Robert (Richard Jenkins).
When Robert and Nancy marry and move in together, Brennan and Dale are forced to live with each other as step brothers. As their narcissism and downright aggressive laziness threaten to tear the family apart, these two middle-aged, immature, overgrown boys will orchestrate an insane, elaborate plan to bring their parents back together. To pull it off, they must form an unlikely bond that maybe, just maybe, will finally get them out of the house.