How do I get rid of my adult pothead step-son who is a mooch?

My step-son is a total momma’s boy. He quit high school 2 years ago and has not worked a day since. All he does is sit in his room all day smoking marijuana, playing video games, and drawing cartoons. My wife and his sister are both enablers and it is a constant battle. The only responsibilities my wife will put on him is to clean the kitchen. He restricts this to one load of dishes and claims he gets weekends off. I have constantly protested this lifestyle, but my wife just protects him from my wrath. HELP!