Because of these pages :
Notice , the sky ?
also ;
Notice , the source of the curse? Where the light is emanating from?
And the page doesn't give any specifics. It just let's us assume.
We can guess that they were exiled sure. BUT, cursed? a whole clan? for something one person did? And why didn't the baby stay with the father?
Now for my reason to think that Von Helson was involved .....
Pay attention to the Young Vampire ( Young VonHelson). Notice that he took damage to his left eye. (apparently ELVEN weaponry can scar/hurt/kill vampires)
Now look at this page of Older Von Helson. Notice his left eye ??!?! IT is gray indicating damage ,plus he is weairing a monocle. ( a vampire that needs glasses?) Come on now.
The only missing link is between Nyx and VonHelson. Or ... there might not be a link at all? Maybe NYX just took advantage of the Kuro clan's misfortune and cursed them. So someday he could use that to his advantage. At least that's my theory.
