Doran Martell

Prince Doran Martell is a member of House Martell, as well as the reigning Prince of Dorne and Master of Coin in King Robert's Small Council.

Background
During Robert's rebellion against House Targaryen, Doran's sister Elia was brutally murdered by Gregor Clegane, who acted on Tywin Lannister's orders. After the rebellion, Robert becomes King and Prince Doran becomes his Master of Coin.

"A Game of Thrones" (298)
In his letter to Eddard Stark, Jon Arryn claims that Robert and his Small Council - including Doran - assassinated Robert's wife Queen Cersei Lannister.