Directed by Adam McKay
Written by Adam McKay and Will Ferrell
Trailer
IMDB

Will Ferrell and John C. Reilly are both living at home with their parents. Will Ferrell's mom gets married to John C. Reilly's father, and they all move in together. Ferrell and Reilly have to share a bedroom.
At first they don't like each other, but eventually they bond over not liking Ferrell's successful brother. Yet, they end up driving their parents apart with their rampant immaturity. Then they decide it's time to grow up and get jobs in order to get their parents back together.
It's a lot more mean spirited than I described. It's also a movie that couldn't have had a full script. If it every word they said onscreen was written on a piece of paper I'd be blown away. Half of the time it seems like they're just throwing random goofy lines out there, but sometimes it works. Another thing that rubbed me the wrong way with this flick is the way most of the actors over-act. Reilly's father is the worst offender of over-reacting. He's like a pissed off cartoon character. Still, I want you to know that this movie is funny. It's at least on the same level as Semi-Pro* and Blades of Glory.

6/10

*After further reflection and a discussion with my girlfriend, I'd have to say that Semi-Pro was better than Step Brothers. Blades of Glory is still a mostly laughless, but inoffensive, affair.