A subsystem is simply a part of a larger system. Families are subsystems of society. Nuclear families are subsystems of extended families. The “husband and wife” or “spousal” unit is a subsystem of the nuclear family. Finally, each individual is a subsystem of the family. Other subsystems include the sibling subsystem, the younger generation subsystem, the middle generation subsystem, the older generation subsystem, the female subsystem, the male subsystem, the nurturing subsystem, the disciplinarian subsystem, etc. Subsystems can even form around interests or hobbies (e.g., the rowdy subsystem, the mellow subsystem, the sports-lovers subsystem, the nature-lovers subsystem, etc.).
Problems occur in the family structure when covert coalitions form between or among subsystems. For example, when a parent and child form a covert coalition against the other parent, the structure of the family is not solid and conflict results.