These little bastards are really good at two things: Guilting parents or others to feel bad and get help, and not appreciating a **** thing that people do for them. They just expect it, like its normal for you to go out of your way like that.I have always told my kids that if you want me to do the job, you are going to help or at least stay out there with me and learn something. Now my fiancé's son sounds like your nephew. He rarely has ever helped me work on his car and until recently, was never appreciative on anything I did on it. For a while I refused to work on it at all. These days I just do it to help her out so she doesn't have to spend the extra money to get it done. He now at least thanks me for working on it.
FYI: I forgot.. The next day after I did his brakes he totalled it. I brought him Honda pads, high quality bendix rotors, and two rebuilt calipers. I did the calipers because I knew two things.. I did not want to tear back in there for anything, so I paid $40 as a form of insurance. And, if one of the calipers was hanging up he would absolutely never no, and when he needed new brakes again, my name would be tossed around by him and his mother. Both ungrateful. He's a good kid though.