Most people are doing something morally wrong by not having children, or only having 1 child. That seems like a reasonable conclusion to me.
However, I wouldn't push the point. My view is that "life is good so having children is good" but not "you must have as many children as possible." There are various ways I might justify this philosophically, but I would just say that parents have a special obligation to their children and, if you have too many children, it's impossible to fulfill that obligation. So you should have as many children as you can effectively parent.
However, I wouldn't push the point. My view is that "life is good so having children is good" but not "you must have as many children as possible." There are various ways I might justify this philosophically, but I would just say that parents have a special obligation to their children and, if you have too many children, it's impossible to fulfill that obligation. So you should have as many children as you can effectively parent.