This study explored multifaceted associations between children's aggressive behaviours and loneliness feelings by identifying sub-groups of children with different individual profiles, and also examined whether profiles associated differently with children's quality of close relationships with mothers and peers. Participants were 145 non-clinical boys (8 to 11 years) sampled from two public elementary schools: forty-one third-graders, fifty-one fourth-graders, and fifty-three fifth-graders. Using k-means clustering methods based on overall teacher-rated aggression and child-rated loneliness feelings, four distinct clusters emerged. Tukey HSD and Scheffe procedures validated the clusters, revealing significant inter-cluster differences on child's secure/insecure attachment to mother and on quality of friendship with a best friend. Discussion focuses on understanding different relationship patterns among these subgroups of school-age boys. (Contains 2 tables.)