Sunspear is located on a peninsula of land just south of the Broken Arm.
A thousand years ago, Dorne was filled with petty, warring lords. When the warrior queen of the Rhoynar of the eastern continent, Nymeria, came with her people to Westeros, she took one of the strongest of the Dornish lords as husband. Lord Mors Martell, with the aid of Nymeria and the Rhoynar, conquered the rest of Dorne. Following the custom of the Rhoynar, the Martells now call themselves Princes. Dorne was the only kingdom in Westeros to be ruled independently from the Targaryens, and did so for 150 years.
After repeated attempts at conquest failed, King Daeron II brought Dorne into the fold by peaceable means, marrying the Prince of Sunspear’s sister and giving his own sister to be the wife of the Prince. Their motto is, “Unbowed, Unbent, Unbroken.”
The current lord of the house is Prince Doran Martell, whose sister Princess Elia was killed in the Sack of King’s Landing and whose uncle Prince Lewyn of the Kingsguard died fighting at the Trident. He has one brother, the notorious and infamous Prince Oberyn Martell, who is called the Red Viper after an incident in his youth when old Lord Yronwood died after duelling with him over Lord Yronwood’s mistress, sparking accusations of the use of a poisoned blade. Wed to the Princess Mellario of the Free City of Norvos, Prince Doran has three children: Princess Arianne is his eldest child and his heir. Before Prince Doran, his mother was Princess of Dorne. She was a close friend to Lady Joanna Lannister, and indeed had tried to marry one of her children to one of Lord Tywin’s twins. He rebuffed her, and always seemed to hold Princess Elia’s marriage to Rhaegar Targaryen as an insult.