SoMany, that's interesting that many of your siblings don't have children, and are unlikely to. As I said up the thread, the four of us have had one child between us - my son - and while it's still possible my brother might have a child, neither of my sisters will.
It's definitely not coincidental. We grew up with a model of the family in which reproduction was involuntary and, if not actively unwanted, was at best something you shrugged about and put up with, like bad weather. We saw our mother have repeated pregnancies and miscarriages, sick and struggling, and frankly, none of it looked like anything any sane person would want to do. It took me until age 40 to decide I wasn't doomed to repeat her life, and my sisters made the opposite decision.
(In fact, I remember posting on Mn before I had my son, after a friend had remarked on how odd it was that none of us had children, asking whether people would find four adult siblings all over 35 who didn't have children by choice unusual, and a lot of people said yes, they would wonder what had made them decide that.)
In answer to whoever asked about whether it was the number of children or the personality of the parents that created the problems in my childhood - you can't extricate the two in my case. My parents did and do love us, but as someone else said, they were on survival mode, just trying to keep everyone fed and clothed. There was no energy left over for attending to any of our emotional needs - I was badly bullied for years at school, by a teacher and classmates, and not only did they not notice, but it never even occurred to me to tell them, because I was aware from a very young age that anything 'extra' I needed just increased the burden on people who were already spread far too thin.
Yes, I think the number of children was the tipping factor, on balance. There would have been more of everything with fewer of us. Yet it's hard to blame my parents as individuals for the religious and social conservatism of 60s and 70s Ireland - they were uneducated, had absorbed the unthinking Catholicism of their time and social class, and had no thought of anything other than trudging on with whatever life threw at them. Unfortunately, we were part of what life threw at them.
(Possible incredible anecdote for anyone who isn't familiar with the history of contraception in Ireland - after her sixth or seventh pregnancy, my mother was seen by a progressive Church of Ireland doctor, who put her on the pill - my mother (who was not consulted) believed it was a vitamin that would stop the miscarriages. )