You know, I kind of think that depending on when Pirates of the Carraibean happened and Jack's age at the time, Jack may be Mary and Edward's child. (Mary's looks and Edward's personality.) Imagine Connor getting faced with him. Better yet, imagine HAYTHAM meeting his long-lost half-brother (because Connor is serious, but Haytham is stuffy).
Also, the treasure medalion things are totally Eden-thingies.