With an adult they could I guess? It's not against the law for someone under 18 to watch a movie is it? I mean would they haul the parent to jail if a 16 year old watched an NC-17 film?
well for me one thing is acting and another watching. If the little kid is actring in a harmless scene, no violence, no... what is the problem? The problem comes when children watch films that aren't suitable for their ages because they don't have the ability to distinguish between fake and real, and don't understand what they are seeing.
Judd Apatow doesn't let his children watch his movies. Not even the parts they're in. I can only assume if the child is the star of the film, that they're allowed to see it. I mean, what's there that they haven't already seen?