He really should be 15.
Because: I deduced that Rood met Kiel for first time when he was 5 years old, a year or so with echanging letters until their mother dies, that would make Rood about 6 then, by the looks of it, Rood lived with Uncle Jerk for at least a half year + and unspecified time when Rood was dead + 8 years from the ritual ~~ roughly 15 years.