...called if they are born of six? Example: Hope from Legacies. Also somebody born of a werewolf, witch, and a vampire? This is for a supernaturally book I'm doing.
That seems to be a made up word, a mix of "hybrid" and numeral prefix. You should have a look at the wiki table on the subject, but the options are likely sexa- or hexa-. As for specific castes, beats me. You're not really obliged to adhere to any etymological processes anyway, it's just fantasy.