The Base Sons are a now organised military force who defend the lives of both bastard-born and low-born individuals. Beginning as a small organised group, they have become an army throughout the third, fourth and fifth seasons. They are made base-born individuals and the Smallfolk, from all across the Seven Kingdoms. Their hidden base of operations is coined as the "Basefort"
The group was created after King Joffrey Baratheon had almost all of King Robert's bastard children killed. They were a small group during the War of the Five Kings, but began strengthening their numbers. They are allies with the Brotherhood without Banners. They claim to have the support of House Harrigon and many lesser houses in the Stormlands, Riverlands and the Reach. By the Red Wedding their numbers reached around 30,000, big enough to win many battles.
Joshua returns to the Eyrie to meet with Lysa Arryn and his half brother Sweetrobin. He begs Lysa the aid of the Vale to help them against their enemies. Lysa however scolds Joshua, telling him the knights of the Vale will fight and die for Sweetrobin, not the bastard son of Lord Arryn. When he returns to camp, he is greeted by two of Lord Walder Frey's bastards, Ryger Rivers and Ser Walvar Rivers. They tell Joshua of House Frey's involvement in the Red Wedding, and that their half brother Tylan Rivers is fighting against Edwyn Frey, Lord Frey's heir. He agrees to fight with them against the Frey's. On their way the Twins, they come across the Brotherhood without Banners. The Base Sons and the brotherhood enter into an alliance. In a strange move, the Base Sons begin making wedding pacts. Their leader Joshua Stone marries Rearna Hill.
- Ser Joshua Stone, a bastard of Lord Jon Arryn and leader of the Base Sons.
- Ser Tyrard Stone, a bastard of Ser Norwin Morvayn, commanded the Base Son's chivalry during the Battle of the Bastards.
- Gomely Greensea, a blacksmith who witnessed the killing of one of King Robert's bastards.
From the North
- Jormon Snow, a bastard son of Lord Jon Umber.
- Harmon Snow
- Larris Snow
- Myle Snow
- Derren Snow, a bastard from the North.
From the Riverlands
- Brendon Rivers, a bastard son of Ryman Frey.
- Ser Wesson Rivers, a bastard son of House Blanetree.
- Ser Walvar Rivers, a bastard son of Lord Walder Frey. He joined following the Red Wedding.
- Ryger Rivers, a bastard son of Lord Walder Frey. Joined following the Red Wedding.
- Dilron Rivers
- Maygen Rivers
- Lorrand Bellsey, a bastard son of King Robert Baratheon from the Riverlands.
- Noella Rivers, a bastard from the Riverlands and the wife of Lorrand Bellsey. She is currently with child.
From the Vale
- Ollas Stone, a bastard of House Hersy.
- Ser Desmor Stone, a bastard of House Nolliner
- Ethon Stone, a bastard of House Sunderland.
- Liya Stone
- Edder Stone
- Derron Stone
From the Westerlands
From the Reach
From the Borderlands
- Garner Ashes, a bastard from the Borderlands.
From the Stormlands
From the Crownlands
- Ser Pharrel Waters, a bastard of House Thorne.
- Ser Waylar Waters, a bastard from the Crownlands.
- Merry Waters, a bastard from the Crownlands
- Ethon, the unacknowledged bastard son of Dyron Blackgard. Left the Base Sons after joining the Wastelandic Zul Joriin.
- Sarina Waters, a vigilante better known as "the Raven", the eldest bastard of King Robert Baratheon. She is not a full member of the Base Sons, but maintains a loose association with them.