My DH and I have been together since we were 19 & 21, and were on the fence for years if we'd ever have kids. We were the couple that would have been fine either way; we'd be happy with kids but wouldn't have been devastated if we never had them. Sometime around turning 30, a switch flipped and we decided to give parenting a shot. Life had other ideas though, and it took us two long years to have my oldest. Three years later we decided he needed a sibling, and our family was complete. When my youngest was a newborn my DH went in to get the big V. His doctor asked him if he was sure because, "what if you get divorced?" My DH responded, "Well I'll still have two kids so...."
Long story short, sometimes people do change their minds. And sometimes they don't. I love my kids more than anything and I still stand by the idea that we would have been fine if we decided not to have them.