I don't consider myself the stepson
Background short and sweet:
Lived with Dad since parents got divorced. Dad remarries. Dad's new wife moves in with son. New wife and son take over the house. Wife's son and I fight. Dad's wife and I fight. I move out. Wife's son moves out. GREAT. I need to move back in. Wife's son as well as girlfriend and new baby move back in. Tensions arise again. Girlfriend stays home all day with baby. Girlfriend hardly cleans. Dad and wife expect cleanliness. Wife's son and girlfriend hardly clean. I pile there crap left in common area. Tensions arise. Wife's son starts slamming things around. I feel like kicking his ass but won't. Any advice?