And the exceptions have been explained to you.
The children of aliens, born in the realm, were natural born subjects. They could inherit from anyone. They were full up natural born subjects.
Exceptions to that rule were for ambassadors and invading armies. There was also some variation based on who controlled what land during war.
Obama Jr wasn’t the son of an ambassador. His father wasn’t part of an invading army. If Obama was born in Hawaii, then control of the territory was not open to dispute. If born in Hawaii, he falls under the Founder’s understanding of natural born citizen, because he met the rules for a natural born subject.
Blackstone: "...upon a like defect of hereditary blood, the issue of a denizen, born before denization, cannot inherit to him; but his issue born after, may."
English-born children of aliens CANNOT inherit from their parents, even AFTER their parents become denizens. What about that do you not understand?