Affiliative relationships are well documented in a wide range of wild animals. However, there is limited evidence of their existence in social farm animals, despite potential significant animal welfare implications. We aimed to determinewhether pigs have preferential partners for affiliative interactions and associations andwhether these preferences remain stable over time or are influenced by sex, dominance rank or litter of origin (i.e. kinship or familiarity). Two pens of 12 domestic pigs, Sus scrofa, twomales and two females from three litters, were weaned at 28 days of age and observed from 42 to 57 days (postweaning phase) and from 70 to 85 days (finishing phase) following a change of housing at 62 days. Sociopositive behaviours, including nose-to-nose and nose-to-body contacts, allogrooming and associations while lying were scored on video observations over 6 days per phase. Using social network analysis methods, we found nonrandom social preferences for allogrooming in both pens of pigs, which remained stable between the postweaning and finishing phases.We also observed nonrandom associations for proximities while lying, although these patterns were not found in both pens of pigs and did not systematically persist between phases. In contrast, nose-to-nose interactions were expressed randomly in both pens and phases. Depending on the housing conditions, social preferences for grooming interactions or proximity while lying were only weakly influenced by sex, dominance rank or litter of origin. We did not find any correlation between social networks for grooming interactions and associations while lying. In summary, our study highlights the existence of durable affiliative relationships based on grooming interactions and proximity while lying within stable pig groups. These relationships appear to be minimally affected by sex, dominance, kinship or familiarity. Taking these relationships into account, particularly from a young age, could be pivotal in improving the welfare of pigs on farms.