I’ve had the question asked quite often since DD was born - the first was the midwife wheeling me from delivery room to postnatal after the birth from hell! I generally just ignore the question. I don’t want another child. I don’t want to go through all that again.
Do get a bit
about the people who suggest having a sibling to share the load of caring for elderly parents. I’m fairly sure that’s one reason why my parents (both onlies) had a second child. And my brother has been absolutely useless in doing anything about caring for either parent.
Have a second (or more) child(ren) if you want them and can afford them. But definitely not to either provide support for looking after ageing parents and not to provide a sibling for the existing child(ren).