@b in Brazil we don't have "middle name" as a category, but I have two "first names" and sometimes the second one gets filed as a middle name in Canadian forms (kinda annoying because it clashes with e.g. my passport). In my case the two names are what we would call a "composed first name" but all my maternal grandmother daughters have "<name> of <Virgin Mary denomination>" as their first name, where the saint reference reads more as "middle name" to me.