House Baratheon of Dragonstone

When the Usurper's War ends and Robert takes the Iron Throne, he hands out rewards to his own. His brother Stannis gets Dragonstone, the island where the Targaryens first landed in Westeros, in 284 AC. Stannis takes it almost as an insult — he would rather have had Storm's End, the seat of his own blood — but Robert needs someone he trusts holding that rock.

Three years later he marries Selyse Florent, a match with no warmth on either side. In 289 AC, when the Greyjoys rise against the Iron Throne, Stannis commands his brother's fleet as Master of Ships and leads it to victory at the Battle of Fair Isle. The marriage will produce a daughter, Shireen, but between Stannis and Selyse there is never anything beyond duty done.

Stannis is the first to doubt that Queen Cersei's children are also Robert's. He looks into it together with the Hand of the King, Jon Arryn, and the two of them agree that Stannis will take Arryn's son, Robert, as a ward at Dragonstone. They plan to speak with the king as soon as he returns from Winterfell.

They never get the chance. Arryn is poisoned before that conversation happens, and Stannis sails back to Dragonstone to call his bannermen. By the time he can return to King's Landing, Robert is dead too, leaving a realm with no clear heir and on the edge of war.

Stannis sends letters across the realm proclaiming himself king and calling Cersei's children abominations, born — he says — of incest with her own brother. Around this time he replaces his sigil with the flaming heart of R'hllor, the Lord of Light: he has converted to that faith at the urging of the priestess Melisandre of Asshai.

He readies himself to face his other brother, Renly, who has crowned himself king in his own right, but a shadow kills Renly before the battle, and much of Renly's bannermen switch to Stannis's side. His court splits between the Queen's Men, who pray to R'hllor, and the King's Men, loyal to the Seven.

Defeat at the hands of House Baratheon of King's Landing at the Battle of the Blackwater forces him to retreat to Dragonstone.

Davos Seaworth manages to convince the king not to stake everything on Dragonstone and instead sail to the Wall, to help a Night's Watch that can barely hold on.

There, Stannis's army defeats the Free Folk in battle, and the king begins working to win over the northern lords one by one, with some success among them.

Meanwhile, Dragonstone, the fortress that gave this house its name, falls into the hands of the Iron Throne: the king loses his own seat while he fights other battles elsewhere.

Stannis marches his army against Winterfell, held by House Bolton, to take it. Meanwhile, his wife, Queen Selyse, betroths several of his knights to wildling women, in an attempt to seal an alliance with the people from Beyond the Wall.