You'll have to point that part of the Constitution out to me because I can't see where it defines natural born citizen at all.
Congess has legislated that a natural born citizen is one born in the United States and subject to our laws. The 14th Amendment says the same thing. If Obama was born in Hawaii then he certainly meets that requirement. And the Supreme Court ruled in an 1898 case that the citizenship of the parents was irrelevant, that if the child is born in the U.S. to parents who are citizens of another country, that person still is a natural born U.S. citizen. Justice Gray, writing for the majority, stated:
"The foregoing considerations and authorities irresistibly lead us to these conclusions: The fourteenth amendment affirms the ancient and fundamental rule of citizenship by birth within the territory, in the allegiance and under the protection of the country, including all children here born of resident aliens, with the exceptions or qualifications (as old as the rule itself) of children of foreign sovereigns or their ministers, or born on foreign public ships, or of enemies within and during a hostile occupation of part of our territory, and with the single additional exception of children of members of the Indian tribes owing direct allegiance to their several tribes. The amendment, in clear words and in manifest intent, includes the children born within the territory of the United States of all other persons, of whatever race or color, domiciled within the United States. Every citizen or subject of another country, while domiciled here, is within the allegiance and the protection, and consequently subject to the jurisdiction, of the United States. His allegiance to the United States is direct and immediate, and, although but local and temporary, continuing only so long as he remains within our territory."
If Obama was born here then he's a natural born U.S. citizen. And if you think the Supreme Court is going to take this case up, or overturn precedent going back 110 years and throw the 14th Amendment out the window, then you're deluding yourself.
Shades of Dred Scott. Look at your definition for a moment and take a look at someone like Rudy Giuliani. Second generation Italian-American on both sides of his family. By your definition, unless you can prove that all four of Giuliani's grandparents were naturalized as U.S. citizens before Giuliani's parents were born then either Guiliani's mother or father or both were not born U.S. citizens. And in that case, unless you can show where they went through the naturalization process then they never became U.S. citizens. And therefore Giuliani himself, by your definition, cannot be a natural born U.S. citizen because both his parents were not. Now, does that make any sense at all to you?