Peer-support services enhance mental wellbeing and increase the knowledge and capabilities of self-help groups in various settings. To ensure that these services foster peer-support relationships as intended, it is necessary to design and assess them from a relational perspective. This study presents a relational framework for peer-support design and its application to two existing peer-support services for solitary seniors in Seoul and Ulsan. The framework aims to support the analysis and conception of peer-support services. It incorporates network analysis and codesigning to understand multi-faceted peer-support relationships and to develop strategies for creating relational values, respectively. Case studies used observation and interviews to understand the multi-faceted issue of social support. Relational data for fourteen solitary seniors were collected and analyzed in terms of the qualities, quantities, and structure of peer-support relationships. Analysis results demonstrate an increased level of perceived peer support through relationship forming, as well as the factors that suppress peer-support building such as network fragmentation and the discrepancy of needs. Analysis results were fed into codesigning interventions with stakeholders. Based on these findings, we discuss the preconditions for building peer-support relationships and outline the relational approach to the design for peer support in a wider context.