What Grounds Special Treatment Between Siblings?

Siblings ought to treat one another specially – in other words, siblings qua siblings ought to treat one another in ways that they need not treat others. This paper offers a theory of why this is the case. The paper begins with some intuitive judgments about how siblings ought to treat one another and some other normative features of siblinghood. I then review three potential theories of why siblings ought to treat one another specially, adapted from the literature on filial piety: the gratitude theory, the friendship theory, and the special goods theory. In each case, these theories fail to explain some of the intuitive judgments about how siblings ought to treat one another. The paper then proposes a familial belonging theory. The institution of the family has certain goals, which impose normative demands on family members. I suggest that one such family goal is that every member feel familial belonging towards every other member, a goal which grounds the ways in which siblings ought to treat one another specially.