On the obscure planetDathomir, the title of "Sister" was used, regardless of actual kinship, as a form of address for a witch, alone or followed by her first name.[1][2][3] Sometimes, this title was also applied to offworlders, out of affection or respect—Augwynne Djo once called PrincessLeia Organa "Sister Leia".[1]
The first Dathomiri witches were all biological sisters, born to the wayward JediAllya,[1] whence the metaphorical use of "Sister" amongst them. Additionally, the sisters referred to their leader as "Mother", further developing the metaphor of the family.[3]