Final answer:
In Greek mythology, Zeus is considered the grandfather of Calchas. As a seer with exceptional abilities, Calchas' divine ancestry is traced back to Zeus through his father Thestor and further back to the roots of the Greek pantheon.
Step-by-step explanation:
The divine being considered to be the grandfather of Calchas is Zeus. In Greek mythology, Calchas, the famous seer of the Trojan War, is the son of Thestor and his lineage can be traced back to the king of the gods, Zeus, through his grandfather.
This connection to Zeus places Calchas in a lineage of divine ancestry and gives context to his exceptional prophetic abilities. The history of the Greek pantheon tells that the primordial deities Gaia and Uranus were the progenitors of the Titans, who in turn were ancestors of the Olympian gods, including Zeus.
A variety of texts outline the lineage of Greek mythical figures and their connections to the gods. Calchas' insights and foresight are often attributed to his divine heritage, emphasizing the significance of lineage in Ancient Greek culture. The concept of a human having a relationship with a deity, whether through lineage or favor, is a recurrent theme in many cultures and mythologies around the world.