I don’t want to be a doomsayer, and I really do hope I’m wrong about this MBS, but more than likely this will never end unless the boy dies.
I know that no two situations are alike, but I think all of us have some experience with parents who baby their kids into disaster.
My brother (who’s around 15 years older than me) was married and had 2 kids around 1964. 1973 his wife is killed in a car accident, he’s left with 2 kids a very full-time job and with complete devastation at the loss of his wife. For about a year he moved back in with my parents (I was still living there at the time) not so much because he had to financially but just because he wasn’t able to adequately run a house by himself. He’s a smart guy but his marriage was a very 1950s traditional marriage, he brought home the bacon and she ran the house and did the “work” aspects of raising the kids. A guy who had never done his own laundry or cooked anything other than a boiled egg was in no shape to raise two kids.
After a year he gets married again to a woman who has a step son who’s about 13.
My brother’s wife (they’re married to this day) is a great woman, very nice etc. She just is a horrible mother, has never disciplined her son once. It was through a miracle of god he graduated high school. Since that time he’s lived 95% of his life with my brother, in the basement, smoking pot and getting drunk. In between living with my brother he’s been married 5 times. Each marriage ended in divorce because this guy has never been disciplined and, he thinks he’s allowed to beat his women whenever he wants and does. His mom finds ways to get him out of legal trouble, usually by more or less bribing the women by giving them all of the marital assets and then some in the divorce, which brings Johnny back home again. I should also mention for every one of these marriages they (my brother and his wife) have bought him either a small house or mobile home to live in. So that’s 5 residences they’ve bought and had to give up because of this guy in lieu of him getting in trouble for beating up his wives (he has spent a few months in jail, actually.)
In should also mention this guy has never had meaningful employment.
Why’s my brother put up with it? No idea. He chose his life and he has to deal with that.
I hope to god this doesn’t happen to you, but in my experience mom’s who baby their children like this never let go. I have a friend (to add to the list of anectdotal evidence) who raised a similar kid, he’s been living with mommy and daddy his whole life and he’s 31. They continue to have to bail him out of jail every few months, finance his life, and etcetera.
All I can say is, if the problem is here now then it’s not going to go away just when he’s 18. You need to find a way to either deal with the fact that you’re going to be financing this guy and probably living with him for your entire life, find a way out, or find some way to stop it without losing your marriage.
You’re not in an enviable position, every option has pretty shitty results.