Joffrey Baratheon was the Crown Prince of the Seven Kingdoms, and became king when his "father" King Robert died. He is a short tempered, cruel boy who is married to Sansa. He kills Ned Stark stating that he performed acts of treason, and is unaware that Jaime is actually his father, therefore, he is not the rightful king.

Game of Thrones Quotes

Tyrion: Let me give you some advice bastard. Never forget what you are. The rest of the world will not. Wear it like armor, and it can never be used to hurt you.
Jon: What the hell do you know about being a bastard?
Tyrion: All dwarfs are bastards in their father's eyes.

Baelish: Do you know what the realm is? It's the thousand blades of Aegon's enemies, a story we agree to tell each other over and over until we forget that it's a lie.
Varys: But what do we have left once we abandon the lie? Chaos, a gaping pit, waiting to swallow us all.
Baelish: Chaos isn't a pit, chaos is a ladder.