To explore the role of public health nurses (PHNs) in Norwegian primary school health services in supporting siblings who have a brother or a sister with complex care needs. A qualitative, exploratory design using focus groups combined with visual methods. Nineteen Norwegian PHNs participated in three focus group discussions between May and September 2022. The nurses were asked to draw themselves as PHNs working in primary schools. Braun and Clarke's reflexive thematic approach was used to analyse the transcribed interviews. The drawings were analysed using critical visual analysis methodology. The findings revealed that PHNs in primary schools focused on establishing good relationships and found it important to be flexible and creative. However, a challenge to successful service provision in supporting siblings and their families was that the nurses lacked support for the implementation of health promotion interventions and often felt alone. The analysis elicited three main themes: 'the importance of relationships and flexibility in meeting siblings' needs', 'feeling alone with responsibility for supporting siblings' and 'the forgotten children: a need for coordinated services'. PHNs in school health services are in a unique position to provide support to improve siblings' mental health and well-being. To fully benefit from PHNs' potential to support siblings, there is a need to clarify guidelines and develop evidence-based interventions. This study provides valuable insights for health authorities, educators and practitioners on what inhibits sibling support in Norway. The study highlights the potential for PHNs to play a significant role in delivering timely health-promoting interventions for these siblings in school settings independent of context. This study was reported in accordance with the Consolidated Criteria for Reporting Qualitative Research (COREQ). No patient or public contribution.