Most theories of parenthood assume, at least implicitly, that a child will grow up to be an independent, autonomous adult. However, some children with cognitive limitations or psychiatric illness are unable to do so. For this reason, these accounts do not accommodate the circumstances and responsibilities of parents of such adult children. Our article attempts to correct this deficiency. In particular, we describe some of the common characteristics and experiences of this population of parents and children, examine the unique aspects of their relationships, review several philosophical accounts of parental obligations, consider how these accounts might be extrapolated to semiautonomous adult children, and provide suggestions about parental obligations to promote autonomy and independence in adult children with cognitive limitations or psychiatric illness. In extending accounts of parental responsibilities to the case of semiautonomous adults, we find that the parental role includes the duty to continue to provide care—indefinitely if necessary—while cultivating autonomy and independence.