In the context of boundaries in a family system, describe internal boundaries.

Answers may vary. Boundaries, a central concept in family systems theories, can be likened to abstract dividers that function (1) between and among other systems or subsystems within the family and (2) between the family and the environment. All families develop networks and relationships between coexisting subsystems that can be formed on the basis of gender, interest, generation, or functions that must be performed for the family's survival (Minuchin, 1974). Members of a family may simultaneously belong to numerous subsystems, entering into separate and reciprocal relationships with other members of the nuclear family, depending on the subsystems they share in common (e.g., parents, mother and daughter, brother and sister, father and son), or with the extended family (e.g., grandmother and granddaughter, uncle and nephew, mother and son-in-law). Each subsystem can be thought of as a natural coalition between participating members.
Other subsystems or coalitions, especially partner or spouse, parental, and sibling subsystems, are more enduring in nature. According to Minuchin (1974), the formation of stable, well-defined coalitions between members of these vital subsystems is critical to the well-being and health of the family. Minuchin points out that the clarity of the subsystem boundaries has far more significance in determining family functioning than the composition of the subsystem. The relative integrity of the boundaries of spouse or partner, parental, and sibling subsystems is determined by family rules.