It may to surprising to learn that tough-on-immigration Mitt Romney is part Mexican. Romney's great-grandparents were polygamous Mormons who left the United States and settled in Mexico because the U.S. was not a big fan of polygamy. Romney's father George was later born in Mexico.
While Romney's grandparents eventually moved back to the U.S., others in the family remained, so he now has second cousins in Mexico.
Incidentally, the following CNN report mentions that George Romney ran for president in 1968. If he was not born in the U.S., how was he able to run for President?
Well, Wikipedia writes that "questions were occasionally asked about Romney's eligibility to run for President due to his birth in Mexico, given the ambiguity in the United States Constitution over the phrase "natural-born citizen."
However George Romney's grandparents never gave up their U.S. citizenship when they moved to Mexico, so his parents were citizens, and so was he. The Constitution states:
The children of citizens of the United States that may be born beyond the sea, or outside the limits of the United States, shall be considered as natural-born citizens of the United States.
So there you go. Here is the report: