In BDSM, a person within the kink community or in a particular House / Tribe who is seen much like a sibling to those they are close to. Usually they are feminine-identified or feminine-presenting; the masculine counterpart being Brother. There is a deep emotional bond, though typically not romantic. The dynamic may or may not be sexual in nature, depending on the people involved.
Sister can also reference a role play dynamic, potentially where two or more feminine or female-identified littles interact with a shared Caregiver / Big.
