Well it takes place thousands of years before the first series and time travel is involved: the Scub is a far more recent phenomenon, it's before the world was reshaped by the Scub Coral, the heart carving hasn't happen yet (and won't happen for a long time), and we don't know if Renton or any of Gekkostate got brought into past like Eureka so they won't exist for thousands of years.
Originally Posted by LordTerminal
Though the possibility now exist that Renton is his own ancestor.
Joris: Your story makes me want to have a little brother, Papycha. Isn't that weird?
Kerubim: Don't worry, Jojo. You have your whole life to meet new brothers. Some you will choose, others will ruin your life, and others still will make it worth living...