>> his mother was 18 when she gave birth, too young to convey citizenship. <<
Neither common law nor natural law, as discussed by Sen. Howard’s speech introducing the 14th amendment and innumerable 19th-century court cases would in any way require a mother to be 18, or any age, to convey citizenship. <<
>> and his father was never a citizen <<
But he was married to one, making it evident that he intended, at the time, to be an immigrant, not a wayfaring traveler.
Now, had his mother stayed in Indonesia, you might have a tenuous argument that she surrendered her citizenship, and through her, he did. But this argument would be very tenuous indeed, because it is in fact at the core of the very first Supreme-Court decision related to immigration, wherein the daughter of a Brit who returned to Britain was ruled to be a citizen by birth.
Your best bet would be to say he renounced his citizenship, and that the fact that he claimed to be an immigrant confirms that he thought of himself as having renounced it.
look it up.
in order to convey citizenship from Dec. 24, 1952 and prior to Nov. 14, 1986:
“Citizen parent physically present in U.S. or possession 10 year prior to childs birth, five of which after age 14.”
http://photos.state.gov/libraries/unitedkingdom/164203/cons-acs/transmission_tables.pdf
being married to one is irrelevant.
just the facts