Not true. I don't remember any point of the rules saying that, on patreon there are literally dozens, if not hundreds of games with such content and no one makes a problem. The only thing they pay very strict attention to is the actual appearance of children in the game so that it is not misinterpreted, although if you stick to the right line then even that is acceptable, e.g. a mother holding a child in her arms in the epilogue etc.