Distinguishing kin from non-kin is central to theories of family, reciprocity, and care, yet empirical research typically relies on self-reported survey categories that obscure extended family ties. This paper demonstrates the substantive value of population-scale networks by using a complete, sociocentric family network of the Netherlands to re-examine who “non-kin” caregivers actually are. We link the population-wide family network to administrative records of all government-compensated informal elder-care relationships (ages 65+), allowing us to measure genealogical distance between caregivers and care recipients across the entire population rather than within egocentric samples. This population-scale approach reveals that around one-third of caregivers labelled as non-kin in administrative and survey contexts are in fact extended kin—individuals only two steps away in the family network, such as affinal relatives linked via children or grandchildren. These extended kin are structurally far closer than the general population and display caregiving patterns that are markedly more family-like than those of true non-kin, including higher care intensity and greater likelihood of co-residence. By contrast, true non-kin caregivers are rarer than commonly assumed and face distinct constraints, including greater geographic distance and age-related barriers. Across all categories, caregivers are disproportionately female, of lower socio-economic status, and more likely to have a migration background. Methodologically, the analysis illustrates how linking administrative care records to whole-population networks can resolve long-standing measurement problems in family sociology and provide a new empirical foundation for studying care, obligation, and social support