Deyen?

Translations can vary depending on what the person thinks fits best. If the translation is a Korean name but the translater wants to alter it a bit for it to become more of an English name, they can do that. I'm guessing Dion is an alteration of Deyen, I'd have to check the original though.

That’s the problem. In the same chapter they alternate Deyen with Dion. For example when Roxanna was talking with Maria, Maria was calling as Deyen and Roxanna called him Dion. So, I thought that maybe it’s how his mother calls him.