Using the controversy surrounding marriage with a deceased wife’s sister that occupied Presbyterian and Congregationalist theologians of the early Republic, this essay explores the eroticization of the sentimental family and the contours and crises of the incest prohibition in the wake of the Revolution. The essay begins by tracing the history of ecclesiastical trials of incestuous marriage in the Presbyterian church, arguing that the failure of the synods and General Assembly to offer definitive judgments of such marriages suggests a tension in the force of a transcendent incest prohibition. Two cases from the late 1820s, in particular, gained national attention in both the theological and secular press, and force the Presbyterian church to explore the legitimacy of their incest prohibition, and exploration that lead, ultimately, to a constriction of the incest prohibition as written in the Westminster confession of Faith. I then turn to the conjunction of kinship, sexuality, and sentiment that animates the texts comprising the controversy and argue that, in an effort to defend an expansive interpretation of the Levitical incest prohibitions these theologians were among the earliest writers to argue that sentimental, affectionate relations between family members were inherently erotic. In this sense, the family becomes the primary site for the deployment of sexuality. Such a concern about the incestuous nature of family relations, in turn, forced theologians to consider the problem of incest in the postlapsarian origins of society.