User blog comment:Kaido King of the Beasts/A Rival for Luffy/@comment-72.168.160.8-20160119220811

I always figured Law and Kid would be Luffy's pirate rivals, echoing the Roger-Whitebeard-Shiki triangle. You can even see the parallels between Law/Whitebeard and Kid/Shiki. Law and Whitebeard both wield abilities regarded as the "Ultimate Paramecias" and both represent the friendlier side of their respective rivalries. Kid's and Shiki's abilities both revolve around manipulating objects and are on the less friendly side of the triangle. As for the Marines, I figure Coby fits the Garp parallel best, not having any DF abilities and being around the same age as Luffy.