II Antonia II
I notice the only way we know to escape from the curse is to be half-breed (Cresento : father elf + human mother ; Cordell : father vampire + mother elf).
Maybe the curse is the discrimination toward other races ?
Personally, Cresento and Cordell probably escape the curse from the luck for having a parent (while in Cresento's case, his grandpa is lucky too) who isn't a cursed Kuro elf. Like so 50/50 chance and they won the luck.
So yeah maybe that and with luck, too.