I'm not at all interested in FF as a series (in fact, I only paid for XIV after giving it three chances and it was mostly the presence of friends in the game that got me to stay). I'd say the only reason I know anything about the past titles has been just absorbing it over time that I've been playing video games in general.
If someone who's 12 and is playing XIV as their first MMO, I could see how they might not know anything about FF games earlier than, say, XIII.
If someone who's 12 and is playing XIV as their first MMO, I could see how they might not know anything about FF games earlier than, say, XIII.