Speaking of Robin, in comparission, Oden is to Yamato whay Olvia is to Robin.
Yeah, is right there, what Olvia and Oden did its very important to the main plot, and Robin is following her mother's steps and completing the journey she couldn't.
And that's the same with Yamato, she's following Oden's steps, and plans to complete the plans of the Dawn, that Oden couldn't.
But we're missing the Jaguar D Saulo of Yamato, there has to be someone before Oden and Ace, that taught Yamato to keep believing and be hopefu, someone with which Yamato has an actual emotional attachment.
And you guys remember that one time we saw the Scabbie-Kids stealing money from Yasuie?
There was Izou right there, but most of us thought, nah that's just Kiku, just to actually get bamboozled right afterwards.
Well, this could be what's happening here, that one shadow in Kin'emon memories,(that unlike King and Queen's shadows, it doesn't have any light at all on its face), it looks a lot like Jack, but it cannot be Jack, so maybe the reason why it looks soo much like him, its because is a relative of Jack(older brother, father, etc).
And considering Yamato and Jack are the exact same age, is possible they grew up together like Law and Baby 5.