What is it that makes someone a parent? Many writers--call them 'monists'--claim that parenthood is grounded solely in one essential feature that is both necessary and sufficient for someone's being a parent. We reject not only monism but also 'necessity' views, in which some specific feature is necessary but not also sufficient for parenthood. Our argument supports what we call 'pluralism', the view that any one of several kinds of relationship is sufficient for parenthood. We begin by challenging monistic versions of gestationalism, the view that gestation uniquely grounds parenthood. Monistic and necessity gestationalism are implausible. First, we raise the 'paternity problem'--necessity gestationalists lack an adequate account of how men become fathers. Second, the positive arguments that necessity gestationalists give are not compelling. However, although gestation may not be a necessary condition for parenthood, there is not good reason to think that it is sufficient. After further rebutting an 'intentionalist' account of parenthood, in which having and acting on intentions to procreate and rear is necessary for parenthood, we end by sketching a pluralistic picture of the nature of parenthood, rooted in causation, on which gestation, direct genetic derivation, extended custody, and even, sometimes, intentions, may be individually sufficient for parenthood.