Dorne was a sovereign kingdom before the invasion of Aegon the Conqueror and remained one afterwards, the only one of the Seven Kingdoms to do so. It joined the Seven Kingdoms through a peaceful marriage alliance nearly two centuries later. House Martell have been the Lords of Sunspear (and the Princes of Dorne) ever since. Sunspear has no lord at present, as its former lord, Prince Doran Martell, was killed, along with his heir, Prince Trystane Martell.