I have no idea AT ALL where to start in explaining to DS (6) about this, and last night he asked the question - "what's sex?" because of a throw-away line on tv. He knows where babies come from, just not how they get there in the first place. He even knows about menstrual cycles, as he was 4 1/2 when DD was born, and talking about it seemed very natural at the time.
But we need help in telling him about the sex bit, as we really don't want to freak him out, but we don't want him hearing about it in a skewed way in the playground. I'd be very grateful for advice on how to approach this, and any recommended books.