"Isaac" could refer to many things:
* A person: Is this a person you know? To determine their tribe, you would need more information about their background or heritage.
* A fictional character: If Isaac is from a book, movie, or game, the tribe they belong to would be part of the fictional world's lore.
* A Biblical figure: Isaac is a prominent figure in the Bible. He is considered a patriarch of the Israelites, but he did not belong to a specific tribe himself.
Please clarify who or what "Isaac" refers to so I can help you further!