But yeah, it was just too hard to fit more characters without it looking weird. Jasmine herself references Ami and Vera, and Oalston's in a Hautley flashback. Only Bosche, Nobumasa and Siegfried are yet to be mentioned in some form or another. Elina isn't mentioned herself, but her science loving younger relative, Markim, is all over the place in the game.
In terms of other relatives, there is Vahn's grandson Alduin who rules Ivalice, Ami's granddaughter, and Vera's cousin as well.