1.Multiple historical influences:
Kinship terminology, according to some researchers, is a product of historical accident; the kinship terms that a particular people employ and societal changes affecting these terms are mainly the result of cultural borrowing and of modifications imposed upon indigenous systems by local conditions. Alfred Kroeber, a proponent of this view, described a finite series of logical distinctions that could be employed in the construcvtion of a nomenclature system – for example, distinctions in terms of age, sex, Generation or collateral line (1909). Kroeber never suggested a set of rules that might enable us to predict which distinctions a particular people would employ. This is understandable in terms of his conviction that kinship terminology is essentially a matter of historical accident. G.P.Murdock pointed to a major flaw in this “historical “approach to kinshipmay take an infinite number of forms , where there is no limitation on the number of possibilities, cross-cultural similarities may usually be attributed to Diffusion. But where the forms of behavior are limited, similarities should be expected in many societies irrespective of historical accidents and connections (or the lack of them). The specific kinship terms that people employ clearly vary from society to society, but the methods of classification are few. Since there are only a limited number of terminological systems we must assume that we are not dealing with an accident prone phenomenon ( Murdock 1949: 113-117).
2.Morphological differences in language:
Some scholars consider kinship nomenclature to be more a linguistic than a social phenomenon – that the terms people employ are a function of their language above all else (Gifford 1940: 193-94). The particular terms that people employ must conform in structure to the principles underlying their language but the way in which relatives are classified does not have any necessary relationship to these principles, AS Murdock pointed out, it is no accident that we find the same type of kinship classification among peoples speaking different languages, just as we may find different nomenclatures being employed by peoples who speak the same language (1949: 117-18). Since this is so we must reject the view that there is something inherent in language that determines the way in which kinsmen will be classified.
3.Elementary psychological processes:
Alfred Kroeber once suggested that, ‘‘terms of relationship reflect psychology, not sociology” (1909: 84). What he meant was that kinship terms reflect a way of thinking and that nomenclature systems are predicated upon certain fundamental psychological processes. We can assume that certain relatives are referred to by the same term because they are thought of as being similar in crucial ways . To the extent that psychological principles apply to all humans, however, they cannot account for cultural differences. It is not possible to account for cultural variation in terms of factors that are invariable or universal. If different kinship nomenclature systems reflect different psychological processes, on the other hand, then it is processes that guide their thought (Mrudock 1949: 119-20)
4.Universal Sociological Priciple : RC Brown , Edward Sapier etc..(Levirate & sarorate
5.Customs of Preferential Marriage: Bilateral , matrilateral and patrilateral cross cousin marriages