it will be explained later in the story. But currently, there is no other "Gran" in the universe. There are 2 "versions" of him because the people from Grancypher (Cagliostro) and Rhodes Island (Amiya) have different memories of "Gran". While the current "Gran" is neither of both. He's a new slate, which is constantly pulled by both worlds trying to claim him back.

Why thank you! Hope you'll enjoy the story!