RELATIONSHIP is a vocabulary for describing relationships between people:

friendOf, acquaintanceOf, parentOf, siblingOf, childOf, grandchildOf, spouseOf, enemyOf, antagonistOf, ambivalentOf, lostContactWith, knowsOf, wouldLikeToKnow, knowsInPassing, knowsByReputation, closeFriendOf, hasMet, worksWith, colleagueOf, collaboratesWith, employerOf, employedBy, mentorOf, apprenticeTo, livesWith, neighborOf, grandparentOf, lifePartnerOf, engagedTo, ancestorOf, descendantOf, participantIn, participant