Seneca asserts in Letter 121 that we mature by exercising self-care as we pass through successive psychosomatic “constitutions.” These are babyhood (infantia), childhood (pueritia), adolescence (adulescentia), and young adulthood (iuventus). The self-care described by Seneca is 'self-affiliation' (oikeiōsis, conciliatio) the linchpin of the Stoic ethical system, which defines living well as living in harmony with nature, posits that altruism develops from self-interest, and allows that pleasure and pain are indicators of well-being while denying that happiness consists in pleasure and that pain is misery. Augustine divides the narrative of his own development into the stages of babyhood (infantia), childhood (pueritia), adolescence (adulescentia), and young adulthood (iuventus) in the Confessions, a text wherein he claims familiarity with more than a few works of Seneca (Conf. 5.6.11). Furthermore, he had access to Stoic accounts of affiliation not only in Seneca’s Letter 121, but also in Cicero’s On Goals, and in non-extant sources of Stoic ethical theory. After pointing out that Augustine endorsed the notion of self-affiliation outside of the Confessions, I raise the question of whether he also makes the notion of affiliation thematic in his philosophical autobiography. I argue that he does indeed present himself and some of his primary relationships – with his mother and his long-term girlfriend – in terms of personal and social oikeiōsis. In addition, his self-critiques in the early books of the Confessions can be more fully understood if compared to Stoic developmental theory. He depicts himself as failing to progress intellectually, socially, and morally: although he passed through the successive constitutions, becoming physically larger and cognitively capable, he did not mature correctly by the standards of his Stoic sources.