Adolescence is a developmental period in which physical-activity habits become increasingly shaped by personal interests, peer relationships, family practices, and growing independence. Parents remain influential, although their role changes as adolescents gain greater autonomy in deciding how, when, and with whom they engage in physical activity. This paper examines the relationship between family exercise modelling and adolescents’ independent physical-activity choices from a developmental social psychology perspective. The conceptual framework integrates social learning theory, social cognitive theory, self-determination theory, family systems perspectives, and research on parental support, modelling, autonomy, and adolescent physical activity. Parents may influence activity through their own behaviour, encouragement, transportation, shared participation, emotional support, and access to opportunities. Existing evidence indicates that parental modelling has a small positive association with youth physical activity, while parental support generally shows a stronger relationship. Meta-analytic and longitudinal research also suggests that supportive parental involvement and shared activity may contribute to sustained participation, whereas highly controlling behaviour may be less beneficial. The framework distinguishes behavioural modelling from parental support, monitoring, pressure, and control. It proposes that modelling may influence independent activity choices through observational learning, perceived competence, internalization of physical-activity values, and access to suitable opportunities. However, adolescents increasingly evaluate whether parental behaviour is compatible with their own interests, identity, goals, and social environment. The manuscript does not introduce fabricated participant data; quantitative findings are drawn from published evidence. Overall, the paper argues that family-based physical-activity promotion should emphasize credible parental modelling, supportive involvement, autonomy support, and opportunities for adolescents to make personally meaningful and increasingly independent physical-activity choices.