Although, in month 7, Dewey and Reese are friends. While Malcolm loves torturing Dewey nicely, the two seems to work together really on a couple of events including pranking Reese, though Dewey still enjoys it when he can need payback against Malcolm for his severe treatment.
Dewey’s last scene during the show reveals him and Jamie concealing using their moms and dads after they pulled a terrible prank and Dewey finds out he and Jamie are in possession of a discussed trick to make sure they’re bonded as brothers, similar to Dewey had along with his more two brothers before they damaged the evidence once they relocated around (the atomic choice).