Yes, snotty, there are some very smug parents of two children on here for sure.
In the real world, there is no such thing as the perfect family size. There are pros and cons to every situation, and so many variables.
I love my DSis. We did play together a lot as young children and it was lovely, but I sometimes wonder if having a ready made playmate got in the way of me developing social skills at times. Certainly, I didn't have my dd's gift for making friends with almost anyone. Nevertheless, it was fun to have another child around at the weekends, on holiday etc. When we weren't fighting, that is....
Unfortunately, we drifted apart as teenagers. I used to get really fed up trailing around after DSis and her all-consuming hobby. I also felt that there wasn't anything I could ever do to impress my parents as DSis had already done it. We weren't close as teenagers and never really talked about stuff.
As adults, we do love each other but we're not close at all. Rather, I'd say we're politely indifferent to each other. We don't live near each other but make an effort to get together because we both have only children of the same age who happen to be really close. If it weren't for the kids, I'm not sure we'd bother.
The burden for looking after our elderly parents falls entirely to me. DSis is neither willing nor able to help.