Your stepson isn't really the problem - your wife is.

For whatever reason, she doesn't seem to want her son to grow up, leave home, and get a life of his own.

Not only that, she is not allowing you to be man of the house. Good luck with this situation; you're going to need it. Unless she stops letting him call the shots, you're probably going to have to resort to moving out before she will listen to you.

Who is paying all the bills in the house? You? If so, you are being taken for a ride. Unfortunately, this appears to have been going on for far too long.

Your wife should not let his wants override you. That's wrong, and that would be a deal breaker in almost any marriage.

You can't keep sucking it up, because that means he'll be living with you when he's 30. It's time for you to draw a line in the sand and set a deadline for him to move. If it were me, I would give him until the end of August - that's it.

You should get counseling with your wife to address how she and her son have treated you over the years. They have shown so much disrespect for you, it's unbelievable. If she refuses to go, then you need to have a plan ready for separation.

Now, I firmly believe that a birth mom needs to put her UNDERAGE child ahead of any non-birth man who may be in her life (date, fiance, husband), but once a child is old enough to make their own way--they should. Obviously, this mother hasn't learned the first rule of being a parent--that your job is to make yourself obsolete. In other words, it's a parent's job to raise their child to be confident, self-sufficient, self-supporting, independent.

I honestly fear there is no answer to your problem, if the boy's mother choses to enable him to be a slug. YOU don't have the power to change things (other than removing yourself from the situation). This mother and son have such a disfunctional, odd relationship, that nothing you do is going to break through to them.

Good luck, though