Doran Martell

Doran Martell is an unseen character in the second season. He is first mentioned in the War of the Five Kings feature in the Season 2 bluray.

Background
Doran Martell is the Prince of Dorne and the Lord of Sunspear. He heads House Martell, the ruling house of Dorne. He's the older brother of the late Princess Elia, who was murdered by Ser Gregor Clegane in the Sack of King's Landing

Season 2
Tyrion Lannister, Hand of the King, proposes a marriage alliance to Prince Doran, offering the hand of Princess Myrcella Baratheon to be wedded to Doran's youngest son, Prince Trystane, when both come of age. Prince Doran accepts the alliance and Myrcella is sent to Dorne as a ward of House Martell.

In the books
In the A Song of Ice and Fire novels, Prince Doran is a cautious, pensive man who does not wear his emotions on his sleeve. He has a bad case of gout and has trouble walking, preferring to move in a wheeled chair constructed by his maester. He hides his disability so as to not appear weak to his potential enemies. He has three children: Princess Arianne, Prince Quentyn, and Prince Trystane, all born of his wife, Lady Mellario of Norvos.