This chapter focuses on the roles that family members and peers play throughout development in optimizing athletes’ opportunities to reach the highest levels in the sport. Research on the earliest phases of expert athletes’ development is often the most challenging to conduct, given that childhood sport experiences typically occur years prior to athletes’ attainment of expert status. Transition from the sampling to the specializing phase is perhaps the most challenging to navigate for young athletes and their key social influences, likely due in part to the significant social, cognitive, and emotional developmental changes occurring during quality time. While during childhood, parents’ feedback is critical to building athletes’ sense of competence and motivation; research among high-performance adolescent athletes indicates parents demonstrate diverse behaviors. Family members and peers also play important roles in expert athletes’ personal and social development throughout the specializing years, espousing values related to achievement, respect, altruism, hard work, success, and persistence.