To borrow terms from RFC 2119, "having a child makes people more responsible" is a SHOULD, but statistically, turns out to be a MAY. (#survivorBias: people are likely to acknowledge this, if they did turn out to actually be more responsible - "turned out GREAT for ME", emphasis added. The other case, not so much.)

However, I feel like the age of a parent is a factor, sure - but it's not an overwhelming factor...