Brennan Huff (Ferrell) is a sporadically employed thirty-nine-year-old loser who lives with his mother, Nancy (Mary Steenburgen). Dale Doback (Reilly) is a terminally unemployed forty-year-old who lives with his father, Robert (Richard Jenkins). When Robert and Nancy get married and move in together, Brennan and Dale are forced to live with each other as step brothers. They immediately don't like each other. Dale warns Brennan not to touch his drum set or else (Brennan feels tempted to do this). Soon after, Brennan finally plays on Dale's drum set and leaves the room before he can return. Dale enters the room and notices a chip on one of his drumsticks and confronts Brennan about it. Brennan denies this and a fight breaks out between the two after Brennan vows and makes good on his promise to "rub my nutsack on your drumset". The fight ends as Dale and Brennan strike each other at the same time with a bat and a golf club. The parents declare that the irresponsible men should find jobs or else they're out of the house. Later on, Brennan's very successful but mean brother Derek (Adam Scott) comes to visit with his family. As Brennan and Dale hide in Dale's tree house, Derek comes to mock Brennan and Dale. Angered by Derek, Dale punches Derek in the face. Brennan is in awe that Dale did something to Derek that he always wanted to do. After this occurred, Derek's long-suffering wife Alice (Kathryn Hahn) finds it arousing that Dale punched Derek, becoming infatuated with him. Both men eventually realize that they have a lot in common, and become best friends.