Ultimate newbie here, but I guess no. I just reviewed the genbukan rules, guidelines and general information last weekend.
If it was important enough for them to print out the whole package for every student, it is probably a good idea to read it front to back.
One of the things I remember is that The highest level you can achieve as a teen is Shodan. You simply have to learn other things like e.g bojutsu until you are old enough to progress beyond Shodan.
So unless he passed level 2-8 within a year of turning 16...
I don't know which X-kan the boy is enrolled in, so it might be different, but even then I assume they don't hand out high level black belts to a kid.
Another limitation is that there has to be a number of years between next dan level. I don't have the book at hand atm, but at the higher levels it is a couple of years. Other organizations could be different, but even assuming that you can rise one level per year, he'd have to have gotten his Shodan at 8 years old.
Of course it could be a non traditional school, but even in those I think it would be unlikely to have a 16 year old 8th dan.
So despite my newbieness in ninpo, I am inclined to say he simply cannot be an 8th dan. I have been known to be wrong though. Especially since the day I became a married man
