The only circumstance where Natural Born Citizenship is required is to be eligible to become President.
I have three sons.
#1 is a US Citizen at birth even though he was not born in the US. His citizenship was derived from one parent, (me) being a US Citizen. He is not a natural born citizen.
#2 was born in the US, so is a US citizen though place of birth AND having one US Citizen parent. He also is not a natural born citizen.
#3 was born in the US, by that time his mother had become a US citizen. He has two US citizen parents and was born in the US. He is a Natural Born Citizen and therefore the only one of my sons eligible to become President
I hope you're not feeding your son this made-up BS.
My understanding is that the only difference between a natural-born citizen and a non-natural-born citizen is that the former was an American citizen from his or her birth and the other one was not and was subsequently granted citizenship.