From Ankeny, after citing Minor:
Thus the Court left open the issue of whether a person who is born within the United States of alien parents is considered a natural born citizenFrom the Georgia hearing
However, the Indiana Court explains that Minor did not define the term natural born citizen. In deciding whether a woman was eligible to vote, the Minor Court merely concluded that children born in a country of parents who were its citizens would qualify as natural born, and this Court agrees. The Minor Court left open the issue of whether a child born within the United States of alien parent(s) is a natural born citizen.Neither of these two found in the Minor decision what you claim is so obvious. Ankeny quotes WKA
The fundamental principle of the common law with regard to English nationality was birth within the allegiance-also called „ligealty,‟ „obedience,‟ „faith,‟ or „power‟-of the king. The principle embraced all persons born within the king‟s allegiance, and subject to his protection. Such allegiance and protection were mutual,-as expressed in the maxim, „Protectio trahit subjectionem, et subjectio protectionem,‟-and were not restricted to natural-born subjects and naturalized subjects, or to those who had taken an oath of allegiance; but were predicable of aliens in amity, so long as they were within the kingdom. Children, born in England, of such aliens, were therefore natural-born subjects. .and also notes that quoted within WKA
III. The same rule was in force in all the English colonies upon this continent down to the time of the Declaration of Independence, and in the United States afterwards, and continued to prevail under the constitution as originally establishedAnkeny concludes
Based upon the language of Article II, Section 1, Clause 4 and the guidance provided by Wong Kim Ark, we conclude that persons born within the borders of the United States are “natural born Citizens” for Article II, Section 1 purposes, regardless of the citizenship of their parents.