If both parents are American and the son is born on American soil he is definitely a " Natural Born American ".

If the father is Kenyan and the mother is American, and the son is born on American soil he is a " Native Born American ".

Only a Natural Born American is qualified by the Constitution to be President.

Benjamin Franklin had the qualifier inserted for the purpose of not allowing someone with a foreign father to have access to being the Commander in Chief, this is well documented .