By all considered theories of NBC I am aware of, you are a an NBC. But you grandfather would not have been under the most authoritative interpretation as I understand it. Other considered theories would have your grandfather as a NBC, assuming you meant he was born in the US of A.
NBC: “natural born citizen”.
Others on these threads have said different, that because my great grandfather came from Italy instead of, say, Spain, and their law considers me a citizen, I have divided loyalties and am not a natural born citizen.
The main question is "Does a foreign law control who is or isn't considered to be a natural born citizen? Suppose Britain and Kenya went by a strict jus solis interpretation, where you had to be born there in order to be a citizen?