This paper explores the impact of sibling relationships on children’s development within the foster care system, focusing particularly on how sibling separation affects children of different ages emotionally, cognitively, and socially. To address this, the study synthesizes existing literature and theoretical models by combining the developmental stages of children with the role of siblings in child development. Findings reveal that sibling separation at different ages leads to distinct developmental challenges: infants experience severe disruptions in attachment and emotional regulation, middle childhood separations hinder cognitive and social skills development, and adolescent separations result in long-term relational and identity challenges. Previous research underscores the importance of maintaining sibling bonds in foster care, highlighting that these relationships can provide crucial emotional support and stability, mitigating the adverse effects of family disruptions. This study emphasizes the necessity for age-appropriate actions and support services in foster care to minimize the detrimental impacts of sibling separation and promote healthy development. Additionally, it calls for further longitudinal studies to track the developmental trajectories of children separated from their siblings and consider variables such as age differences between siblings and the dynamics of step-sibling relationships. This comprehensive understanding is essential for informing policies and practices that enhance the well-being of children in foster care.