Peer sexuality educators' accounts of their work reveal two approaches to empathy with their students: affinity and alliance. "Affinity-based empathy" rests on the idea that the more commonalities sexuality educators and students share (or perceive they share), the more they will be able to empathise with one another, while "alliance-based empathy" is an analytical process of considering the social contexts that shape others' lives. We assess the potential for each source of empathy to equip peer sexuality educators to counter hierarchical models of teaching and learning, effect social change and promote the interests of youth. Because shared identity categories prove difficult to manage and sustain, we find affinity alone does not offer peer sexuality educators lasting opportunities to work with young people. In contrast, developing alliance-based empathy prepares peer educators - indeed, all sexuality educators - to identify inequalities or barriers that others face and seek ways to foster social change. We conclude with recommendations for future research.