Fictive Kinship
Relationships treated, socially, with the rights and obligations of kinship despite having no genealogical or marital basis — 'fictive' meaning constructed through social recognition rather than fake or lesser. Godparenthood (compadrazgo), blood-brotherhood ritual, and 'chosen family' are documented examples; demographers link its rise in industrial societies to the 'beanpole' verticalization of the family, in which longer lifespans and lower fertility leave a shrinking horizontal network of siblings and cousins to carry kinship's obligations.