Eustass Kid is based on real life Pirate William Kidd also known as ‘Captain Kid’.
Similarities between them include:
-Their Name and Epithet;
-Their Sociopathic Mind;
-Their Methods of Torture, etc..
But William Kidd also had a famous pirate as a father. A pirate named ‘Captain John Kidd’.
There is a captain John in One Piece. He was part of the Rocks Pirates that was beaten 38 years ago by Garp and Roger.
Kid is 23 years old now. We know John wasn’t killed during the God Valley incident because it is confirmed that John was actually killed by his own crewmates for refusing to share treasure with them. So John died sometime between 2 to 38 years from the current timeline, because Moria has his corpse. Which gives John enough time to have had Eustass Kid 23 years ago.
What do you think?
*Theory by letsgomina