Using data from the Household section of the Handicap-Santé (Disability and health) survey, (INSEE-DREES, 2008), this article studies kin support arrangements for dependent older adults in France. The first part is descriptive, showing how the care provided by adult children is affected by the parent’s conjugal situation, sibship size and birth order. The second part analyses families with two adult children and shows that the observed differences in care involvement by birth order are due to three factors: differences in individual characteristics between elder and younger siblings, differences in the impacts of these characteristics on the caregiving decision, and a difference in the adjustment of one sibling to the behaviour of the other (endogenous interactions). The impact of family characteristics seems fairly similar for elder and younger siblings, especially the strong tendency for the woman to be the caregiver if her sibling is a man, but the behaviour of the younger children reflects a compromise between the costs and benefits of caregiving. Defining aid more narrowly as help with daily life tasks, just one major explanation of the differences remains: with a given set of individual and family characteristics, there is an asymmetry in adjustment to the caregiving behaviour of the other child.