A gang of inmates who prey on weaker prisoners. The Sisters include their leader Bogs Diamond and muscle Rooster MacBride.

They maintain their dominance in the hierarchy of prisoners by beating and gang-beating new inmates, including Andy, to whom they take a special liking. Andy always fights back even though he usually loses. Andy eventually wins protection from the Sisters after helping the guards with their finances.

Bogs is severely beaten and paralysed by Hadley after he nearly kills Andy. Out of fear, they never target Andy again, and Bogs is transported to a minimum security hospital upstate. With Red stating that, "he lived out the rest of his days drinking his food through a straw".