Early childhood investment, or the lack thereof, profoundly affects later-life outcomes, but whether social welfare protection aimed at encouraging parental investment mitigates or exacerbates inequitable distributive patterns within families remains elusive. This paper examines the response of intra-household inequality among siblings to a cluster randomised unconditional cash transfer programme implemented in some of Zambia’s poorest communities. We find that the transfers led to compensatory investment in higher birth-order children, particularly by meeting their material needs, although we do not observe a consistent pattern of internal restructuring in health and nutrition or education. These findings are robust across a spectrum of subsample analyses. We also provide tentative evidence affirming the conjecture that the transfers had raised parents’ aversion to inequality after three years of programme exposure, while marginally reinforcing their preference for younger and female children. The literature regards birth-order gradients as context-dependent; therefore, our findings may not be applicable to other settings.