As an essential resource for contemporary mental health systems, the life experiences of mental health users and families are increasingly emphasized in system collaboration. However, despite the development of family peer support focusing on experiential knowledge, there is still little related research in Taiwan. Moreover, the formal system has also often questioned the peer knowledge system. Thus, this study aims to explore the practice of family peer support in Taiwan’s mental health system and to enrich the discussion by organizing the local practice narratives. The study starts with practical knowledge of peer support, the process of peer supporters' empowerment, and finally, the reflection of professionalization brought by family peers as experiential experts. This study adopted a constructivist qualitative research methodology and semi-structured in-depth interviews with nine Taiwanese family peer supporters. It aims to analyze the commonalities of their peer support experiences and highlight the differences in their journeys and experiences to depict the experiences of family peer support in Taiwan. Findings identified the connotation of family peer supporters’ practical experience, using a two-dimensional spectrum to locate the concept of peer support that is still ambiguous in the Taiwanese mental health family community. It develops a philosophy of equal exchange in storytelling among family peers and reveals the disclosure techniques in helping and their awareness of practice in peer support. Also, the motivation and changes in the growth of family peers are analyzed from the perspectives of self-help and publicness. Finally, it illustrates the value of caring knowledge and the discursive challenges it faces. Positioning family peers as 'occupying' the remaining territory of the helping professions reminds current professions in the mental health system of peers' parallel professional positions. This study explores the experiences of family peers and the researcher's observations of family members' communities. It discusses how family members with mental illness can serve as 'experiential experts' and bring an important voice to the mental health system. The study will provide insightful reflections on the helping professions working with families and serve as a source of discussion for the family community movement moving forward.