In many welfare states around the world, including Sweden, a central goal of education is to compensate for the influence of family background on academic outcomes and ensure equal opportunities for all. While this relationship is well documented in core subjects, less is known about how family background shapes achievement in physical education and health (PEH) – a subject aimed at promoting lifelong health and inclusion. Understanding this relationship is key to assessing educational equity and strengthening PEH’s role in supporting all learners. Using Pierre Bourdieu’s theory of capital and social reproduction, the study conceptualizes family background as a mix of economic, cultural, and social resources. Drawing on register data from over 1.4 million full biological siblings who completed Year 9 in Sweden between 2000 and 2017, sibling correlations in PEH grades and overall academic achievement (merit value) are estimated across three-year cohorts. This method captures the total influence of shared family factors on school outcomes. Results show that while family influence on merit value remained relatively stable (4 percentage points increase), its impact on PEH grades rose significantly over time (15 percentage points increase). From 2012 onward, sibling correlations in PEH increased sharply and by 2017 nearly matched those in overall academic achievement. This suggests that PEH is now shaped by similar mechanisms of social stratification as other subjects. The findings call for reflection on how PEH assessment may reproduce or resist broader inequalities. To fulfill its inclusive and health-promoting aims, reforms must consider how grading, curriculum, and access to resources intersect with students’ lived conditions. This study provides structural, longitudinal insights to inform more equitable PEH policy and practice.