Anthropological approaches to family and kinship

Family and kinship has been studied under many disciplines; as such the relations between human beings as it regards to their genealogical origins has a varying relationship.

Under the discipline of anthropology, kinship regards relations forged through marriage and arising from descent as being sufficiently important in deciding who is a member of which family; this is in contrast to biological disciplines which define relations through descent and mating (where by only people who share genes are related. As such, more people are related as defined by anthropology than by biology. However, the two forms of definition do not exist in isolation to each other; as such, people may be related to each other both by descent and by marriage if they are from a common descent.

While families can easily define who are its members since more-often-than-not they know each other in details (for example the different children from each nuclear family), definition of kinship is relatively more challenging as one moves away for each nuclear family; this complexity is increased when kinship by affinity (marriage) rather that pure consanguinity (descent) is included.
Definition of a society through kinship offers a tool for organizing all its individuals into distinct social groups. The most basic of these groups is the family; in this, the definition of relationship is concrete, that is, there is a father, a mother and children. Away from the nuclear family, relations become more amorphous; and some are defined differently in different societies. However, so long as it is defined and known, relationships between persons that can be classified as kinship have been recognized as creating obligations between the involved individuals that are stronger than those that would be seen between strangers.
ANTHROPOLOGICAL APPROACHES
Among the earliest researchers to analyze kinship and family from an anthropological angle was Lewis Henry Morgan; this was in the publication Systems of Consanguinity and Affinity of the Human Family of 1871. In this publication, Morgan initiated the use of the term ‘affinity’ to describe a situation where people consider themselves as having kinship despite the fact that they are not biologically related (Trautmann, 2008).
As such, groups of people who may have little or no biological relationship can identify themselves as a distinct social group; and use kinship terminology in regards of each other. Such groups share obligations to each other and are bound by a set of expected responses to various events; these bonds are strong despite the fact that some members are approximated only in terms of marriage (Houseman & White, 1998).
Kinship system
Each of the groups that can define as a distinct social group is bound by a pattern of behavior that is generally acceptable and/or agreed upon as being normal. These practices govern various events that can and do alter the composition of the society and lay boundaries on what should happen and what shouldn’t.
These patterns affect marriage in particular; this is in regards to forms of marriage (e.g. arranged vs. non-arranged), restrictions to marriage (between brother and sister, cousins), and which sexual relation is defined as incest. The construct of kinship system is however subject to a wide range of opinions with some of the commentary being inconsistent from one aspect to the other (Read, 2001).
This is attributed by the fact that while an anthropologist is usually drawn to study a culture or society that is not his/her own (due to curiosity or novelty), s/he usually carries some of the kinship connotation from his/her system of origin (Wallace & Atkins, 1960).
This leads to inconsistency since some definitions are relative from one system to the other; for example,  the title ‘uncle’ may not have the same meaning from system to system; while one may regard an uncle as the “brother of a parent”, other systems may have a wider bracket to include even cousins of the parents.
These inconsistencies have stood in the way of creation of a universal theory of kinship in humans; that there is a similarity among how humans relate to each other if they share such a relationship. George P. Murdock in his 1949 publication Social Structure, compiled sets of data to show that the mutual feelings of kinship originated from a psychological response based on ego and the relations within the nuclear family.