“I was married and naturalized my Chinese wife and her son from another marriage into the USA. We are divorced but remain good friends. My ex-wife will be vacationing in China for 3 weeks and asked that I stay at her house for the duration of her vacation and take care of her 15year old son while she is away. We live in NJ. Are there any legal forms/process we need to fill out that gives me the authority to temporarily care for him?”
You might put together a power of attorney for a limited duration, specifying what you will be able to do – i.e. make medical decisions, sign notes to the school, transport, etc. Search for one on line to adapt to your purpose. Your signatures will probably need to be notarized. If need be, most attorneys can draw up one of these. Be sure to specify the duties and duration.