Cersei Lannister from A Storm of Swords is the daughter of Tywin Lannister and the sister of Tyrion and Jaime. She has been in a long time relationship with her brother Jaime. Myrcella, Joffrey, and Tommen were the result of their union, and are not Robert Baratheon's children (though the realm thinks so). When Joffrey is killed she blames Tyrion and bribes witnesses to testify against him. She even buys Tyrion's sellsword Bron.
