Family support for older parents is often treated as an aggregate transfer from children to parents, although financial support and housework assistance are distributed among siblings within multi-child families. Using the 2014, 2016, 2018, 2020, and 2023 waves of the China Longitudinal Aging Social Survey (CLASS), this study matches respondents aged 60 or older with their two to five living adult children, yielding 39850 family-year observations and 114023 parent-child-year records. It distinguishes participation breadth, within-family share evenness, primary-provider separation, and share differences between financial support and housework assistance. A support-sharing index combines the proportion of participating adult children with a number-of-children-adjusted measure of within-family share evenness. The index describes observed behavioral distributions rather than normative obligations, negotiation, cooperation, or perceived fairness.

The results show that participation broadens and support-score shares become more dispersed for both forms of support. From 2014 to 2023, the support-sharing index for financial support rises from 0.757 to 0.884, while the corresponding index for housework assistance increases from 0.520 to 0.703. After adjustment for family characteristics, the differences between 2023 and 2014 in both component indices and the overall index are positive in families with two, three, four, and five adult children, although they are smaller in five-child families. Family-level total scores for both forms of support show no sustained decline. The findings remain robust to a 500-yuan participation threshold for financial support, alternative score assignments, individual fixed-effects models based on five waves linked through verified respondent identities, and fractional logit models. Estimates within each fixed child-number group provide the most direct evidence against a purely mechanical denominator effect. Hence, declining numbers of adult children alone therefore do not account for the observed aggregate trend.

Financial support consistently shows a higher level of sharing than housework assistance, consistent with the greater divisibility, additivity, and transferability of money and goods across distance. Unadjusted primary-provider separation fluctuates across survey years. The within-family distributions of support shares across siblings become more similar, whereas the unadjusted proportion of families with no overlap between primary providers of the two support types increases by about 1.4 percentage points between 2014 and 2023. After adjustment for family characteristics, however, primary-provider separation increases significantly by 7.2 percentage points between 2014 and 2023.

Within families containing at least one son and one daughter, son-daughter differences vary significantly across survey years in both financial support and housework assistance. In all eligible families, birth-order differences also vary significantly across survey years in both support types. These patterns are nonmonotonic: neither gender differences nor birth-order differences consistently widen or narrow over time. The findings describe observed behavioral distributions. The survey cannot determine whether broader participation and more dispersed shares arise from negotiated coordination, parental mobilization, low-intensity participation, or changes in individual contributions. Policy interventions should identify actual primary support providers and address time-intensive tasks rather than assign responsibility on the basis of gender or birth order. Future research should combine sibling-level longitudinal data with measures of negotiation, fairness, personal care, support quality, and caregiver burden.