“Really? You have nine kids? You know what causes that don’t you?”
Above is the usual response when someone finds out that I have nine children. Sometime I get very positive responses and occasionally borderline, if not outright, offensive responses, mostly though, just disbelief then a question about my awareness of human reproduction. I have a few pat responses that I use, depending on the person and their comment, but I never try to explain. People who are incredulous don’t want or care about why.