User blog comment:The ASL Pirates/Traveling Back/@comment-10543621-20150720063525/@comment-24.235.56.170-20150721015731

Who's to say it was even four of them in the last generation? The "four emperors" is just what they call them now, because there are four of them. It's true that until there's another pirate king to completely upset the balance, it'll probably remain four, since whoever beats one would presumably become an emperor by default.

But that doesn't necessarily mean that there were always four top players vying for the title of Pirate King. It could have been three, or two, or five. And who's to say they were even called emperors last time? If there weren't four, the world may have decided to name them something catchier than "Sanko" or "Rokuko" ... In fact, given that the world only really got psyched about piracy after Roger's death, it may be that no one cared enough to name them at all.