Juliet Mitchell's wide-ranging theory of lateral dynamics proposes that displacement by a sibling, real or potential, upends a small child's identity and position as “the baby.” This trauma gives rise to the complex process of forming a personal identity in a world of similar others. The impact of lateral relationships should therefore have major implications for analytic practice. Traditionally, however, psychoanalysis has treated siblings mainly as rivals for parental love and attention, not as unconsciously meaningful beings in their own right. This paper describes some ways that Mitchell's theory has inspired clinical interventions that would not have come into focus through a lens of parent–child relatedness.