House Baratheon of Storm's End is one of the Great Houses of Westeros and the youngest of the nine, founded in the first year After the Conquest by Orys Baratheon, bastard half-brother to Aegon the Dragon and the first Hand of the King. While Aegon and his sisters bent the Reach and the Westerlands to dragonfire, Orys was given the stormlands to take. He met Argilac the Arrogant, last of the Durrandon Storm Kings, in single combat outside Storm's End and slew him; thereafter he took the slain king's daughter Argella to wife, raised her up from his prisoner to his lady, and adopted the stag, the words, and the seat of her line. The crowned stag of the Durrandons has flown over Storm's End ever since.
For three centuries the lords of Storm's End served the Iron Throne as Wardens of the storm coast and as kin to the dragonkings, holding the Stormlands in trust through the Dance, the Blackfyre risings, and the long peace that followed. Lyonel Baratheon, called the Laughing Storm, was numbered among the fiercest knights of his age and broke nearly every lance laid against him at the great tourney at Ashford Meadow. Two generations later Lord Steffon Baratheon, cousin to mad King Aerys II, was lost with his lady Cassana when their carrack the Windproud foundered in the teeth of Shipbreaker Bay within sight of Storm's End, leaving his three sons orphaned to a fostering at the Eyrie and the Vale.
The eldest of those sons, Robert, has since won the Iron Throne. With his warhammer he dashed Prince Rhaegar's chest to ruin on the rubies of the prince's armor at the Trident, and with his queen Cersei Lannister he wears the crown the rebellion bought him. The line has flowered into three branches: Robert and his children sit the Iron Throne at King's Landing, his brother Stannis was given Dragonstone and made master of ships, and his youngest brother Renly remains the Lord of Storm's End and master of laws. So is House Baratheon, in the year A Game of Thrones opens, at once the royal house of the Seven Kingdoms and the great house of the storm coast.