Bilineal and bilateral descents are two distinct ways societies trace kinship, each with unique implications for social organization and individual identity.

Bilineal Descent is a relatively rare system where an individual traces descent through both the mother's line and the father's line, but for different purposes. For instance, a person might inherit property or land rights through their mother's lineage, while inheriting ritual status, clan membership, or political office through their father's lineage. It's not simply recognizing both parents, but rather assigning specific, distinct social functions and inheritances to each parental line. This system creates a complex web of affiliations, where an individual's rights and obligations are bifurcated based on the specific context. An example might be found in some groups where certain spiritual roles are patrilineally inherited, while access to specific agricultural lands is matrilineally determined.

Bilateral Descent, in contrast, is a more common system, particularly prevalent in Western societies. In a bilateral system, individuals trace kinship equally through both parents, recognizing relatives on both the mother's and father's sides as equally important. This creates a 'kindred' – a network of relatives that is unique to each individual and typically includes all living relatives from both sides of the family up to a certain degree of relatedness. Unlike unilineal systems (patrilineal or matrilineal) which form corporate groups, a kindred is not a corporate group; it does not own property or act as a political unit. Instead, it serves as a flexible network of support and social interaction. For example, in many modern societies, an individual considers their maternal grandparents and paternal grandparents, as well as their aunts, uncles, and cousins from both sides, as equally significant relatives, participating in family gatherings and offering mutual support without a strict division of roles based on the parental line.