<p>Primates are characterized by complex social systems that influence their dispersal patterns, group stability, and mating strategies. Despite the benefits of cooperation, high levels of inbreeding in social primates can reduce individual and group fitness, leading to the evolution of inbreeding avoidance mechanisms. Callitrichid primates (marmosets and tamarins) exhibit substantial variation in their social organization and extent to which each sex disperses. To examine how reproductive structure and dispersal shape genetic relationships in white-footed tamarins (<i>Oedipomidas leucopus</i>), we estimated genetic relatedness in 84 adults from 31 groups across 13 sites using 12 microsatellite loci. Intragroup relatedness was high (mean R = 0.27, standard deviation [SD] ± 0.25), consistent with second-order relationships on average, and significantly greater than intergroup relatedness at the same site (R = −0.08 ± 0.2). Spatial structure analyses revealed that the influence of reproductive structure on relatedness shapes low levels of genetic differentiation at small geographic scales (&lt;6 km). Females showed significantly higher within-group relatedness (R = 0.35 ± 0.27) than males (R = 0.22 ± 0.26), which is consistent with a greater tendency for male dispersal (i.e., greater female philopatry) and the role of males in inbreeding avoidance. These results reveal a trade-off between inbreeding and sex-biased dispersal as evolutionary strategies. This provides a framework for understanding group composition in the Callitrichidae family. Furthermore, relatedness estimates and reproductive patterns can be used to inform group formation and control inbreeding in ex situ conservation programs and preserve the genetic diversity and composition of populations in the wild.</p>