In the U.S. it is unlawful to film/photograph nude persons under the age of 18, even if they are your own children. Possession of such images is unlawful, no matter how you came to possess them. Parents who have photographed their children while playing in the bathtub, or a naked toddler's backside while doing something silly, (i.e., "innocent" photos), have been threatened with prosecution. Unfortunately, what is seen as innocent by some, is a turn-on to perverted others.

Even non-photographic artwork can be charged as pornography if it depicts under-age persons in a state of nudity. I imagine that, under certain circumstances, even stick-figure drawings may be ajudged pornographic.

I am not sure if an emancipated minor, such as a married 17-year old, is considered an adult under the porno statutes. (Restrictions against under-age drinking and voting are not relieved by emancipation!)