Objectives: Exploring relatives' experience of interaction with other relatives when writing a diary for the critically ill patient. Research methodology: Qualitative interview data were analysed using a phenomenological hermeneutical approach building on the theory of Ricoeur. Setting: Seven relatives, who had written a diary when their close relative was admitted to the intensive care unit at a regional hospital in Denmark, were interviewed after the patient had been discharged. Findings: Writing a diary for the critically ill patient implied creating the story together, which impacted the relationships of the relatives. However, the relationship between relatives determined who might author the diary and also the content of the diary. Authoring the diary could be both a powerful position to shape the story unfolding in the diary or a burdensome responsibility. Conclusion: Authorship of the diary provided relatives with the power to influence the narrative in the diary. Co-authoring the diary allowed the relatives to incorporate the illness experience into a personal narrative, thereby influencing the formation of a family narrative. However, difficult relationships kept relatives from sharing emotions and understandings and could cause suffering among relatives and co-creation of the diary to fail. (C) 2016 Elsevier Ltd. All rights reserved.