Family networks are widely assumed to be a key source of support for older people in Indonesia and Southeast Asia more generally, although empirical study of their composition and functioning is in its infancy. This paper draws on ethnographic and survey data collected in longitudinal research of ageing in three rural Indonesian communities, in order to identify demographic and social factors limiting the size of elders' networks. Gaps in networks commonly emerge as a result of childlessness, migration and alienation, but their implications for older people's vulnerability are shaped by socio-economic status, reputation and cultural norms.