Why does my step son have so much attitude

[Zeppellinnn]

Hello everyone,   I am a step mom of one little boy of 7 years of age.  And a mother of 2 of my own children.  My step son has little to no emotion when he gets into trouble.  But he will fight and mouth off.  He doesn’t cry,  nor seems to care about what’s going on around him.   He talks back,  he pees in his closet and all over his clothes.  And eggs his father on.  I don’t know what to do anymore.  I’m lost for how to help him.

[Sandman2]

Oh, this is sad.  I feel for both you and the little guy!   How long have you been living with him?  
Does he have the same "pee" problems at school?
How old are your two kids and how well do they get along with him?