You cannot say you've raised multiple children in the same environment. The introduction of the second child means it isn't the same environment as when you raise the first. Additionally, the time you've spent between children means the environment has likely changed - and it should, as you grow as a 'human being' and things change. From finances to your hobbies, to your spouse's interests and work, it is not the same environment. That being said, of course some of it is nature. I don't believe Jeff would argue against that.