India’s ageing population faces unequal future kin-based support

India’s ageing population relies heavily on kin, but conventional ageing measures do not capture older adults’ kin networks. We use demographic kinship models to estimate biological and selected affinal kin for a woman aged 65 in 17 Indian states covering 92% of the population, for rural and urban areas, from 1950 to 2100. We find between- and within-state inequalities in kin networks, similar to cross-country differences in South Asia. Kin networks become smaller and older, and working-age kin per older person (support ratio) declines faster than total kin. States reach low kin support ratios decades apart. The support ratio in urban Kerala is expected to fall below one by 2035, but Madhya Pradesh does not reach this level until 2050. Urban Madhya Pradesh is expected to have about 22 kin per woman in 2080, similar to urban Kerala in 2026. However, Madhya Pradesh is projected to have a support ratio of 0.64 in 2080, compared with 1.21 in Kerala in 2020. A male-biased sex ratio at birth associated with son preference has created a deficit in working-age daughters, reaching 10% in Punjab and Haryana around 2040 despite an assumed SRB of 1.05 after 2026. Yet having more sons than daughters does not translate proportionately into more daughters-in-law, traditionally expected to provide care. Our data show 0.6-0.7 daughters-in-law per son in urban Punjab and Kerala. These changes reshape the demographic basis of family support and highlight the need to strengthen formal care systems and redistribute support equitably across kin and genders.