Based on the nature of stands it's pretty much impossible for two people to have the same stand though. The stand stats are pretty much meaningless since they didn't even get stats until right before Part 6 happens.the concept of the arrow wasn't invented yet. remember when dio was talking about how he discovered the world's power? previously hed been using it as a punch ghost just like jotaro, and then he tapped into its main ability. jotaro had always had the potential to manifest the same ability. stands have a specific stat called "growth potential" that shows up in the interstitial/commercial break screens and refers to how much more about the user's ability could evolve or develop. look at koichi, or rohan. its separate from the arrow.