The Three Sisters are a group of three islands—Sweetsister, Longsister, and Littlesister—found in the Bite, located south of White Harbor and north of the Mountains of the Moon. The islands owe loose allegiance to House Arryn of the Vale.
The Three Sisters are within the dominion of the Vale of Arryn and are ruled by House Sunderland. Houses Borrell of Sweetsister, Longthorpe of Longsister, and Torrent of Littlesister are sworn to the Sunderlands. The Three Sisters are sworn to House Arryn of the Vale, but the Eyrie's grasp upon the islands is tenuous at best.
Beacons burn along the shores of the Three Sisters to warn passing ships of danger. The Night Lamp of Sisterton is a prominent beacon operated by House Borrell. Some disreputable Sistermen use false lights to lure ships into wrecks to take their cargo.
The Sistermen of antiquity worshiped the Lady of the Waves and the Lord of the Skies instead of the old gods of the children of the forest, who had been adopted by the First Men of mainland Westeros. The Sistermen of that time cast dwarfs into the sea as an offering to the gods. Septons stopped the practice after the coming of the Andals and the arrival of the Faith of the Seven, however.
The Sistermen of old were a free people ruled by local kings. These pirates and raiders sent longships into the Bite, the narrow sea, and the Shivering Sea to reave and capture slaves. Raiders from the Three Sisters once captured the Wolf's Den and made it their toehold in the north, and Sistermen also raided the eastern coasts of the riverlands. King Theon Stark conquered the three islands at some point.
In retaliation for the raids, maesters say that two thousand years ago the islands were conquered by the north in an invasion known as the Rape of the Three Sisters. The Sistermen bent the knee to the Eyrie to expel the northmen, ending the era of native kings on the Sisters. The Kings of Mountain and Vale from House Arryn and the Kings in the North from House Stark fought over the Three Sisters for a thousand years in the War Across the Water, depleting much of the islands' resources. The largest port of the Three Sisters, Sisterton, remembers the northern invasion and some Sistermen still resent northmen.
The Three Sisters have been a haven for smugglers for centuries. Instead of piracy, the Sistermen have turned to wrecking.
During Aegon's Conquest, the Sistermen rebelled against Ronnel Arryn, King of Mountain and Vale, declaring Marla Sunderland as their queen. She was deposed, however, when a Braavosi fleet hired by House Stark at the behest of Aegon the Conqueror approached the islands. Lord Steffon Sunderland bent the knee to House Targaryen and ended the Sistermen's Rebellion, while his sister Marla ended her days as a silent sister.
Led by the Sunderlands, the Three Sisters supported Rhaenyra Targaryen against Aegon II Targaryen during the Dance of the Dragons, along with the Arryns. The Winter Fever struck the islands late in 132 AC. When the Vale of Arryn broke out into civil war after the passing of Lady Jeyne Arryn, the Three Sisters supported Ser Arnold Arryn.
The Three Sisters suffered after the Sunderlands dragged the islands into two of the unsuccessful Blackfyre Rebellions against the Targaryens. Lord Sunderland attended the wedding tourney at Whitewalls.
A Game of Thrones
While in White Harbor, Ser Rodrik Cassel suggests hiring a fishing sloop out of the Three Sisters to transport him and Catelyn Stark to King's Landing. Catelyn instead chooses Storm Dancer, a galley out of Tyrosh.
A Clash of Kings
Ser Davos Seaworth is sent by Stannis Baratheon with a chest of letters to spread word of Joffrey Baratheon's illegitimacy. His route is to sail to the Three Sisters and other harbors along the narrow sea.
A Dance with Dragons
When Salladhor Saan decides to leave the service of Stannis, he sets Davos loose in a boat, with Davos eventually washing up on Sweetsister. Rather than turn Davos over to Lord Triston Sunderland, Lord Godric Borrell allows Davos to continue on to White Harbor.
—thoughts of Duncan the Tall
—thoughts of Davos Seaworth
Storms were sacred on the Sisters before the Andals came. Our gods of old were the Lady of the Waves and the Lord of the Skies. They made storms every time they mated. These kings never bother with the Sisters. Why should they? We are small and poor.
- A Dance with Dragons, Chapter 9, establishes Sisterton on the island Sweetsister, while the Map of the North in the same book shows Sisterton on the central island. However, The Lands of Ice and Fire labels the central island as Littlesister and the easternmost island as Sweetsister, while keeping Sisterton on the central island.
- A Dance with Dragons, Map of the North
- A Dance with Dragons, Chapter 9, Davos I.
- The Mystery Knight.
- A Clash of Kings, Chapter 23, Jon III.
- The World of Ice & Fire, Beyond the Free Cities: The Shivering Sea.
- The World of Ice & Fire, The Vale.
- A Dance with Dragons, Chapter 29, Davos IV.
- The World of Ice & Fire, The North: The Kings of Winter.
- The World of Ice & Fire, The Riverlands.
- The World of Ice & Fire, The Reign of the Dragons: The Conquest.
- Fire & Blood, Birth, Death, and Betrayal Under King Jaehaerys I.
- Fire & Blood, The Dying of the Dragons - A Son for a Son.
- Fire & Blood, Under the Regents - The Hooded Hand.
- Fire & Blood, The Lysene Spring and the End of Regency.
- A Game of Thrones, Chapter 18, Catelyn IV.
- A Clash of Kings, Chapter 10, Davos I.