Joffrey Baratheon is the King on the Iron Throne. His mother Cersei Lannister will act as Queen Regent until he comes into his majority. He is betrothed to Sansa Stark. He is widely believed to be the son of Cersei and the late Robert Baratheon but was actually fathered by Jaime Lannister. He has Eddard Stark executed for challenging his legitimacy. He is a cruel and sadistic ruler so you might want to be on his good side.