So many people have strong feelings about what age you're supposed to be to have children, and it probably just comes down to when they did it. They probably also believe that they know how many you should have and what you should feed them. But I don't think everyone comes down on the side of thinking you shouldn't be having "so many" kids "so young." I am 43 and have an almost four year old and a nine year old and I look young-ish for my age but I have had multiple people ask me if I'm their grandmother. And I suppose I shouldn't be bothered by that as I am certainly of an age that I could be a g'mother to a 4 year old, and I suppose it is biologically possible to be a 43 yo g'ma to a 9 yo, too.
And I'm jealous of you, too! Whenever I think of the fact that my little guy is only gonna be 40 when I'm 80, it creeps me out. I don't want to be old when they're still young. I feel like generations are really meant to be more like 20 years, but that may be because the last few generations in my family were.