Background <p>Families with exceptional longevity often experience delayed onset of age-related diseases and reduced mortality across generations—a pattern influenced by shared genetic and behavioral factors. While several studies have focused on the members of longevity-enriched families (LEF), little is known about the health trajectories of the spouses marrying into these families. Given prior evidence of substantially reduced mortality among spouses of LEF members, determining whether this advantage reflects selection, shared environments, or behavioral convergence is essential for understanding the mechanisms that underlie intergenerational health transmission.</p> Methods <p>We conducted a multigenerational, retrospective matched cohort study using nationwide Danish civil and health registers. We identified 4378 spouses of LEF offspring and 5378 spouses of LEF grandchildren and matched each of these to ten married population controls by sex, birth year, and year of first marriage. Health outcomes were assessed before and throughout marriage, and after divorce, including hospitalizations by major disease categories, cancer incidence, alcohol-related disorders, as well as cause-specific and all-cause mortality. Educational attainment and familial predisposition for longevity were evaluated as potential explanatory factors. Stratified Cox regression and negative binomial models were used.</p> Results <p>Spouses of LEF offspring and grandchildren demonstrated broadly better health than in matched controls. Throughout marriage, they experienced up to a 25% reduction in all-cause mortality and lower risks of hospitalization, lifestyle-related cancers, alcohol-related disorders, and mental and behavioral disorders. Mortality advantages persisted after divorce. Before marriage, spouses of grandchildren redeemed fewer prescription medications, suggesting better baseline health. These advantages were not explained by higher educational attainment or familial predisposition for longevity. Effect estimates were consistent across outcomes and generations, although they attenuated in the younger grandchildren-spouse cohort, likely due to shorter follow-up.</p> Conclusions <p>Spouses marrying into longevity-enriched families exhibit a substantial and broad health advantage that is not attributable to shared genetic predisposition to longevity or socioeconomic differences. These results are consistent with phenotypic assortative mating, convergence of health behaviors within couples, or a combination of both. Our findings suggest that intergenerational clustering of exceptional health extends beyond genetic inheritance and highlight spouses as an important, previously understudied, component of research on longevity-enriched families.</p>