Final answer:
Cadmus and his siblings were born in Phoenicia to King Agenor and Queen Telephassa, as part of Greek mythology.
Step-by-step explanation:
Cadmus and his siblings were born in an interesting mythological context which oftentimes blends various family trees and geographic origins due to the interconnected nature of myths. However, it is generally accepted that Cadmus, known for founding the city of Thebes and introducing the Phoenician alphabet to Greece, was born in the region known as Phoenicia in Eastern Mediterranean. His parents were King Agenor of Tyre and Queen Telephassa, and Cadmus is one of several important mythological figures born to them.