A study tested hypotheses derived from relational models theory on how four models - communal sharing, authority ranking, equality matching, and market pricing - are used to structure relationships in different types of social groupings. Portuguese participants rated 10 relationships on the Modes of Relationships Questionnaire and reported their shared group memberships. The four-factor structure of the models was confirmed, and a bottom-up approach identified families, friendships, and organizations as the main distinct types of social groupings. The main results showed that relations within families combine mostly communal relations with authority between age groups, whereas relations in organizations combine mostly market relations with authority between age groups as well as professions. Friendships feature a mix of all models, except authority.