The fact that this character is called
Silvio does not mean there is not a Russian form of this name.
Silvio is a form of
Silvius and the Russian form of
Silvius is Сильвий. Every Slavic language will have a form. As an example, my first language is a Slavic one(Polish) and our form of this name is Sylwiusz. It's not really used but this translation exists.