Kinship is a structured system of relations in which individuals are connected to each other by interlocking links and branches, but do not produce social aggregates. It is not a social group. This links constitutes a net of culturally recognised genealogical relations. Kinship includes three main types of tie: first, affiliation, clearly biological, is an offspring transmitted by matrilineality and/or patrilineality; second, brotherhood; and third alliance with another kinship net mainly through marriage, which is the result of the regulation of sexual relations.
Family is a social group characterised by common residence, economic cooperation and reproduction (socialisation and biological), while marriage is a set of practices focused on the relationship between adult sexual partners. Families design several culturally diverse institutions to regulate sexual relations, which are based in sexual division of labour. The monogamous family is extensive but does not have universal character and includes polygamous family including polygyny and polyandry. Beyond this diversity, some characteristics define family. Its origin is in marriage (monogamous or polygamous), consists of husbands, wives and children and is a binding legal tie with rights and obligations that create a precise rights and sexual prohibitions network and a variety of psychological feelings.
In contemporary societies, new forms of kinship are expanding traditional boundaries and questioning their ideological foundations. The contemporary relationship can be divided into different systems. On one side are real relationships based on "blood" where members share genes. On the other side is fictitious kinship that can include relations based on imagined ties and legal rules that permit adoption or patronage, spiritual relationships by joining certain social groups (secret societies, religious orders, etc.) and metaphorical kinship (patriotic, national, ethnic and so on).