Uncle in the context of "Aboriginal Australian elder"

Family (from Latin: familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictability, structure, and safety as members mature and learn to participate in the community. Historically, most human societies use family as the primary purpose of attachment, nurturance, and socialization.

Anthropologists classify most family organizations as matrifocal (a mother and her children), patrifocal (a father and his children), conjugal (a married couple with children, also called the nuclear family), avuncular (a man, his sister, and her children), or extended (in addition to parents, spouse and children, may include grandparents, aunts, uncles, or cousins).

In the lineal kinship system used in the English-speaking world, a niece or nephew is a child of an individual's sibling or sibling-in-law. A niece is female and a nephew is male, and they would call their parents' siblings aunt or uncle. The gender-neutral term nibling has been used in place of the common terms, especially in specialist literature.

As aunt/uncle and niece/nephew are separated by one generation, they are an example of a second-degree relationship. Unless related by marriage, they are 25% or more related by blood if the aunt/uncle is a full sibling of one of the parents, or 12.5% if they are a half-sibling.

The avunculate, sometimes called avunculism or avuncularism, is any social institution where a special relationship exists between an uncle and his sisters' children. This relationship can be formal or informal, depending on the society. Early anthropological research focused on the association between the avunculate and matrilineal descent, while later research has expanded to consider the avunculate in general society.

A cousin is a relative who is the child of a parent's sibling; this is more specifically referred to as a first cousin. A parent of a first cousin is an aunt or uncle.

More generally, in the kinship system used in the English-speaking world, cousins are in a type of relationship in which the two cousins are two or more generations away from their most recent common ancestor. In this usage, "degrees" and "removals" are used to specify the relationship more precisely.

An avunculate marriage (or uncle/aunt-niece/nephew marriage) is a marriage with a parent's sibling or with one's sibling's child—i.e., an uncle or aunt marrying their niece or nephew. Such a marriage may occur between biological (consanguine) relatives or between persons related by marriage (affinity). In some countries, avunculate marriages are prohibited by law, while in others marriages between such biological relatives are both legal and common, though now far less common.

If the partners in an avunculate marriage are biologically related, they normally have the same genetic relationship as half-siblings, or a grandparent and grandchild—that is they share approximately 25% of their genetic material. (They are therefore more closely related than partners in a marriage between first cousins or between granduncle/grandaunt and grandniece/grandnephew, in which on average the members share 12.5% of inherited genetic material, but less than that of a marriage between, for instance, cousin-siblings, in which the partners share 37.5% of their inherited genetic material.)