On the subject of the VK character name spellings:

I am aware that some of the foreign releases of VK have different spellings, occasionally even a mix of them. It's due to translators in some of the countries not always checking the official info from Japan, and thus writing it differently.
I am also aware that wikipedia sometimes says things different from the official info, but that would be because anyone can edit wikipedia, and thus you must rely on the japanese info rather than on it if you want official info. ;

The spellings for the names of the VK characters have been decided in Japan a while ago already, and have been used on merchandise for quite some time. Those spellings were then compiled on the official site when the first season of the anime was released. Hino-sensei confirmed them all again in the fanbook, more recently.

For the most part, I stick to the official spellings, except with Kaname's family name and some other cases. I will never get used to calling him "Clan", so I just stick to "Kuran", but I use the official spellings for the other characters.

Here are the official spellings:
Cross (instead of Kurosu).
Clan (instead of Kuran, but I'll stick to Kuran because Clan is weird. XD;)
Idou (instead of Aidou, but like with "Kuran", I still stick to "Aidou" instead because I like it better that way.)
Cain (instead of Kain).
Luca (instead of Ruka).
The other names are all the same as you have seen before, those are the only ones that are spelled in a different way.

These are the official spellings decided by Hino-sensei and confirmed in the official Vampire Knight fanbook.
(A guidebook for the series, published in Japan).

I'm not saying you must use the official spelling. You're of course totally free to use the official ones or the ones from foreign releases of the books, or a mix from both as you please.
I'm just listing the spellings for the sake of people who might be interested in the official spellings, (and because every so often I get people in western fandoms telling me I spell Luca or Cain's names wrong, when I'm actually just using the official spellings given for them by Hino-sensei... so I thought I might as well explain this here. XD lol)

Every so often I tell myself I should switch to spelling Kaname's family name as "Clan" instead of "Kuran", but, uhm. XD; likes better "Kuran"