I think the fact that Congress passed, in 1790, "An act to establish an uniform rule of Naturalization" that stated : the children of citizens of the United States, that may be born beyond sea, or out of the limits of the United States, shall be considered as natural born citizens indicates that such children were *not* considered natural born under the original understanding of that term. Else why add to the definition? For whatever reason, the words "natural born" were left out of the 1795 act which repealed and replaced the 1790 act. I tend to think it was because they realized they could not define a Constitutional term, except by the amendment process, but that's just conjecture. The provision has not been any subsequent law and so cannot currently be in effect.
That means that the definition remains what it was, and that it did not include children of citizens, even two citizens, "born out of the limits of the United States". The 1795 act merely provided that they were citizens, and the law retains the same provision today.
Thanks.