US Constitution has no mention of “parents”.
Both parents requiring to be NBC is invention of biased people. Obama is living proof, all one needs to be NBC is to possess a birth certificate showing birthplace in United States.
Natural born citizenship had a particular meaning at the time the phrase was used in the Constitution. It had a meaning that was not dependent on any future legislation that might be written. In general terms, it was understood to refer to someone whose citizenship was self-evidently American. If there were competing claims of citizenship that could reasonably be made, such as would arise if one or both parents were foreign citizens at the time of birth, then one was not considered to be a natural born citizen.