I am helping a woman in our church apply for citizenship for her 16 yr old biological son. She was German and just became a naturalized citizen in March 2010. Her son was born in Germany and was 4 years old when they came to the US. There was no father ever documented. We have completed the N-600 form and submitted it and just got a request back for supporting legal documents showing that she has custody of the child. Also there was no 13 digit receipt number (to track the application) on the notice that we received back with the request for the legal documents. Two questions: A. For a biological child, why would they need custody documents? and B. Where and how would you get custody documents? It appears that is all they need to move forward on the application and there is a deadline to respond in 3 weeks. Please help.