His parents were Cuban nationals, he inherited that nationality.
Natural born citizens are naturally citizens because they only have one nationality.
You have a singular definition of natural born citizen.
Since most of the Supreme Court Justices come from Harvard or Yale Law Schools you might expect that any decision reached on any court cases that may possibly reach that level will be decided on a definition that these justices
use.
From a Bing search of the definition of “Natural Born Citizen”:
U.S. citizen at birth
All the sources routinely used to interpret the Constitution confirm that the phrase “natural born Citizen” has a specific meaning: namely, someone who was a U.S. citizen at birth with no need to go through a naturalization proceeding at some later time.
Congress has also ruled that citizenship is subject to certain residency requirements on the parents. Someone born to a U.S. citizen generally becomes a U.S. citizen without regard to whether the birth takes place in Canada, the Canal Zone, or the continental United States.
Reference: harvardlawreview.org/2015/03/on-the-meaning-of-natural-born-citizen