Quiet Sunday Went to Hell in a Handbasket

The day started off so well…. 
I let the boys sleep in yesterday, getting them up around 1pm.  We ate lunch together and I told them to help me get the house picked up.  I also told Brian to go to his room and get a pair of my shoes that I had noticed in there when I woke him up.  He said "Brad’s dog took them in there".  Told him I didn’t care, they were in his room, just go get them. So he goes off on a tangent about how it’s his fault because it was in his room, etc.  I shut him down, told him that he would not show disrespect towards me.  Smart remarks have become common with him lately, and I am tired of it.  Told him that he and his brother will do what they are told, when they are told.  They are grown men, and if they want to live here, they will follow my rules or leave.  I don’t ask them to contribute anything but their assistance on this house and yard, and it’s a constant argument.
So, next thing I knew, Brian was walking out the front door with a duffel bag, saying "I;m not like Brad, I have family to go to", meaning his biological family.  I have my doubts on that score too.  If they wanted him so badly, where have they been the last eighteen years? Hmmm.
At last report from a neighbor, he was camping out at the creek nearby because he had nowhere else to go.  I am a little worried, but not too much. 
At this point, it feels like the boys are trying to test new limits on their "adulthood".  Everyone wants to be the alpha dog around here.  Sorry, but the only alpha is the one who pays the bills and diapered your spoiled butts. 
I am finding it harder to be as upset or anxious as the first couple of times this happened with Bradley.  Brian is just working from that template, and I’m not playing that game.  He’ll be eighteen in just a few weeks.  If he thinks he can make it on his own, or that he will fit comfortably in with his biological family, go for it.  
I’m not stupid, I’ve not only been down this road, I’ve seen others go through it.  It’s nothing more than emotional blackmail on the part of the kids to get their way.  Well, since my kid is essentially and adult now, he can figure it out on his own for a while.  Maybe he’ll learn a little something from it in the long run.  I love my kids, but they have put me through the wringer in every way imaginable in the last year and a half, and I’m just not going to play those games anymore.  Dad is always here if you need him, but not as your doormat.