Tommen Baretheon from A Feast for Crows is the youngest son of Cersei and Robert Baratheon (however, in reality he's the son of Cersei and her brother Jaime). He has been crowned king when his brother dies, but does not have any interest in it at all, after all, he's only 8 years old. Cersei thinks that she will rule in his stead as his reagent, but it does not work out that way for her.
