Comment: From Wikipedia

The Constitution does not define the phrase natural-born citizen, and various opinions have been offered over time regarding its precise meaning. A 2011 Congressional Research Service report stated

The weight of legal and historical authority indicates that the term “natural born” citizen would mean a person who is entitled to U.S. citizenship “by birth” or “at birth,” either by being born “in” the United States and under its jurisdiction, even those born to alien parents; by being born abroad to U.S. citizen-parents; or by being born in other situations meeting legal requirements for U.S. citizenship “at birth.” Such term, however, would not include a person who was not a U.S. citizen by birth or at birth, and who was thus born an “alien” required to go through the legal process of “naturalization” to become a U.S. citizen.[1]

http://en.wikipedia.org/wiki/Natural-born-citizen_clause

Please feel free to read the article and correct my understanding. I love to learn and am no expert on the subject.