Children are at a critical stage of development for cultivating creativity and are highly sensitive to the influence of peers. This study investigated the impact of peer relationships on children's creativity during both cooperative and competitive interactions, using functional near-infrared spectroscopy (fNIRS)-based hyperscanning techniques. A total of 66 children, including 18 familiar dyads and 15 stranger dyads, were recruited to participate in the cooperative and competitive tangram puzzle tasks. The results showed that familiar dyads demonstrated higher originality and lower appropriateness in cooperative tasks compared to stranger dyads. fNIRS data revealed distinct task-specific neural coupling patterns in the inferior frontal gyrus (IFG) contingent upon peer relationship: familiar dyads exhibited enhanced inter-brain synchronization (IBS) during cooperative tasks, while stranger dyads demonstrated stronger neural alignment during competitive interactions. Additionally, positive feedback during cooperative interactions in familiar dyads was significantly correlated with increased IBS in the IFG. These findings underscore the advantages of familiar peer relationships in fostering cooperative creativity and the benefits of strange relationships in enhancing competitive performance. This study highlights the importance of considering relational and contextual factors in fostering children’s creative potential.