The question of if only children are different from children with siblings has been a focus of scholarly and public interest, especially as one-child families have become more common in many societies. This review paper synthesizes English-language journal and scholar-based studies published between 2016 and 2026 on behavioral outcomes among only children compared with children who have siblings. Across the reviewed literature, the strongest and most recent evidence suggests that only children are not globally disadvantaged in behavioral development and, in several domains, show outcomes that are similar to or slightly more favorable than those of children with siblings (Shenoy et al., 2026; Stronge et al., 2019) [7, 9]. 

The review focuses on personality, psychosocial adjustment, prosocial behavior, social competence, academic and cognitive outcomes, and mental health. Although some studies report domain-specific disadvantages, especially in selected cultural or educational contexts, the overall literature does not support the older stereotype that only children are uniformly spoiled, maladjusted, or socially deficient (Associations of only-child status study, 2022; Effects of siblings on cognitive and sociobehavioral development study, 2023). The findings point instead to the importance of context, parenting, family resources, and cultural environment in shaping behavioral outcomes.