I have a 16 year old step son , that its been touble only , doesn't like school, all he wants to do is be out in the streets with his friends and girlfriend , I have talk to him ,but he doesn't want to change his behavior... we have 3 kids more these are mine and my wife's... I live in Washington

And you figuring that taking his last name away from him will be some sort of punishment for his misbehavior?

If he's your wife's son from a previous relationship, how is it that he has your last name anyway?

The short answer is that you have no say in the matter. The operative prefix is "step". It means you have no legal rights concerning this kid. And I seriously doubt that his mother (your wife) could do so either.

When I met my wife he was only 2 years old , the biological basically when he knew that she was pregnant he left... I decided to give him my last name, to make him part of the family.
But my in laws, hate me.. I have always been responsible , never made any differences between him and my own kids, I have talked to him about how school is going to help on his future... but every time Im talking to him he has told me that Im NOT HIS REAL FATHER , because my in laws have told him bunch of stuff... after several years of my in laws telling me that I'm not the REAL FATHER and now him... Im tired and I don't want to do that as punishment... I 'm in the point that I don't want to have any responsibility with him , he thinks his a man , then a man has to be responsible of his own acts... * at his birth certificated there was no father , and he only had my wife's last name... so he never had other last name and no one to claim to be the father.

So you adopted him?

Yes , but my in laws want him to live with them , even thogh they say that Im not his father , they want child support , so basically what I want is take him out of my house and I don't want to give him any money.

If you adopted him (which is the only legal way you could give him your name), he is no longer your step son, but your legal child. Therefore you are responsible for supporting him.

Agree, adopted, he is legally as much your child as ones you fathered.

He is not a step son, and thus I see part of a issue here, if that is how you see him.