The only time “natural born citizen” is used in the Constitution is regarding qualifications for being president. Now, when I was in school, long before this issue ever came up, the teacher said that “natural born” meant both parents were citizens. I would bet that there are old history textbooks around that would say that.
Many of us were taught the same. Unfortunately, government has so managed to blur the lines between the Laws of Nature and the laws of Man that it apparently only takes one natural parent to make a fully natural-born citizen child nowadays.
Go figure.