I think what you're suggesting sounds fine as Worldbuilding tags; there are quite a few tags in already for the history of in-universe organisations, which the Belmont clan would seem analogous to in my eyes from what you're saying. Up to you whether you want to nominate specific characters as well, but I could easily see a case for a combination of tags like (just to give an example) "Worldbuilding: origins of the Belmont clan" and a character tag for the first Belmont vampire hunter being something that people would be interested in offering/requesting.