The Collaborative International Dictionary of English v.0.48:

Kinship \Kin"ship\, n.
   Family relationship.
   [1913 Webster]

WordNet (r) 3.0 (2006):

kinship
    n 1: a close connection marked by community of interests or
         similarity in nature or character; "found a natural
         affinity with the immigrants"; "felt a deep kinship with
         the other students"; "anthropology's kinship with the
         humanities" [syn: affinity, kinship]
    2: (anthropology) relatedness or connection by blood or marriage
       or adoption [syn: kinship, family relationship,
       relationship]

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "kinship":
   accord, accordance, affiliation, affinity, agape, agnation,
   agreement, alliance, amity, ancestry, association, blood,
   blood relationship, bonds of harmony, brotherhood, brotherly love,
   brothership, caritas, cement of friendship, charity, cognation,
   common ancestry, common descent, common source, common stock,
   communion, community, community of interests, compatibility,
   concord, concordance, congeneracy, congeniality, connateness,
   connaturality, connaturalness, connature, connection,
   consanguinity, correspondence, cousinhood, cousinship, empathy,
   enation, esprit, esprit de corps, family favor, family likeness,
   family relationship, fatherhood, feeling of identity,
   fellow feeling, fellowship, filiation, flesh and blood, fraternity,
   frictionlessness, generic resemblance, good vibes, good vibrations,
   happy family, harmony, identity, kindred, like-mindedness, lineage,
   love, maternity, matrilineage, matriliny, matrisib, matrocliny,
   motherhood, mutuality, oneness, parallelism, paternity,
   patrilineage, patriliny, patrisib, patrocliny, peace, propinquity,
   rapport, rapprochement, reciprocity, relation, relationship,
   sharing, sibship, similarity, sisterhood, sistership, solidarity,
   sympathy, symphony, team spirit, ties of blood, understanding,
   union, unison, unity