While the relationship between fathers and sons, real or metaphorical, is still a dominant paradigm among classicists, this paper considers the rival contribution of Roman sons-in-law to the processes of collaboration and succession. It discusses the tensions, constraints, and obligations that soceri–generi relationships involved, then claims a significant role for sons-in-law in literary production. A new category is proposed here: “son-in-law literature,” with texts offered as recompense for a wife or her dowry, or as substitute funeral orations. Cicero and Tacitus are two authors for whom the relationship played a key role in shaping realities and fantasies of advancement. The idealized in-law bonds of De Amicitia, Brutus, and De Oratore are set against Cicero's intellectual aspirations and real-life dealings with a challenging son-in-law, while Tacitus' relationship to Agricola can be seen to affect both his historiographical discussions of father–son-in-law relationships and the lessons he drew from them about imperial succession.