The citizenship question is a "classic" in international aviation law, correct...
(1) the citizenship of the father
(2) the citizenship of the mother (some countries allow that as well)
(3) the country of permanent residence of the parents
(4) the country of departure of the flight
(5) the country of arrival of the flight (where the birth was declared)
(6) the nationality of the airline or operator of the aircraft
(7) the country of registry of the airplane (could be a leased airplane)
(8) the citizenship of the captain
(9) the country of the FIR/UIR where the plane is (or was) at time of birth
(10) and since "England rules the high seas"... British citizenship...
and I probably forget others...
The only problem I personally had, was to correct the original passenger manifest with the cabin supervisor... what did you say we do, list 273 adults, 22 children and 5 infants... or 6 infants... tough question...
And can the new baby claim "air miles" on the frequent flyer program...?