Who was the King of Thebes and brother to Europa?

The King of Thebes who was the brother to Europa is Cadmus. In Greek mythology, Cadmus is a significant figure, known as the founder and first king of Thebes. He is often credited with introducing the alphabet to the Greeks after following a quest to find his sister Europa, who had been abducted by Zeus. His establishment of Thebes included the infamous slaying of a dragon and sowing its teeth, which led to the creation of the Spartoi, a group of fierce warriors.

Oedipus, while also a prominent king of Thebes, is not the brother of Europa. His story primarily revolves around the tragic consequences of fate and his search for truth regarding his parentage. Polyneices, another character, is the son of Oedipus and born into a tragic legacy due to his father's actions. Laertes, on the other hand, is known as the father of Odysseus and does not have a direct connection to the Theban lineage or Europa.

Thus, Cadmus stands out as the correct answer due to his direct relationship with Europa and his foundational role in the history of Thebes.