We are often responsible for the care of others – we find ourselves accepting these responsibilities, and in turn, holding others accountable for fulfilling theirs. Yet while it is clear that we sometimes owe such duties, it is less clear why we owe them. What explains our duties to care? It is this question that I take up. This is a question about normative grounding: it asks why, or in virtue of what, these duties exist. Though not expressly framed in terms of grounding, care ethicists have paid considerable attention to this question – offering either voluntarist or non-voluntarist accounts of grounds. I argue that voluntarist accounts are misguided and turn to non-voluntarist alternatives, which are, in turn, divided between views that trace grounds to (a) certain relational facts or (b) a natural duty. Arguing that neither (a) nor (b) is individually correct, this paper offers a new account: 'hybrid non-voluntarism'. On this view, our duties to care are grounded in a relational moral principle: they exist in virtue of natural duties but are ‘triggered' only by specific relational ties. Through this account, I aim to resolve existing tensions within care ethics and elucidate the grounds of our duties to care.