I have a step son that we have had problems with as well. When a parents only sees thier child a little bit they tend to want to be easier on them. But sometimes that is not the answer. My step son came to live with us about 2 years ago. Before that we only had him every other weekend. He was so disrespectful. After he came to live with us we figured we needed to do something more. We got him counseling. The counselor suggested we think short term. He had us pick a few things My step son liked to do most (tv,video games,etc) and use those as his "reward" for being good. If he was disrespectful and mouthy or in trouble we took all of those "rewards" away for that day. The next day he got to start off fresh. We would give him a warning at first then the rewards were gone. If he got mad we just simply said "you knew the rules and you decided not to follow them, but tomorrow is another chance". It worked for us.