Prior research has consistently demonstrated that socio-economic status (SES) predicts subjective well-being (SWB), and that adaptive cognitive emotion regulation (ACER) is known to serve a protective role in maintaining SWB. However, the mechanism through which SES influences SWB remain underexplored among children, particularly regarding the role of family processes and their interaction with individual regulation capacities across developmental stages. Emerging evidence suggests that the parent-child relationship (PCR) may serve as a critical intermediary, shaping children's emotional development and their ability to engage in ACER strategies. Building on this framework, the present study investigated whether SES indirectly affects children's SWB through PCR and ACER, and whether these pathways differ between primary and secondary school students. Data were collected from a regional sample of 2,315 parent-child dyads (78.3% mothers and 56.1% girls), with parents reporting on PCR and students self-rating their family SES, ACER, and SWB. Path analysis revealed a significant chain effect: SES shaped SWB indirectly through PCR and ACER. Notably, developmental differences were observed in the indirect pathway, with the link from SES to PCR varying between primary and secondary school cohorts. These findings suggest that as children grow older, their SWB becomes increasingly sensitive to the social environment, highlighting the importance of age-specific approaches in family-based interventions.