A family, or group of biologically related individuals, is the basic social unit of all vertebrates. In most animals, the family comprises a female and her dependent offspring. The family unit may be temporary and cease when the young are able to feed and defend themselves. In a few species the young are attended to by both the male and female, but the relationship may still be a transient one, or the relations may be life-long and inter-generational.
Among humans, a family is not restricted to individuals who share DNA. Families are as much social constructs as anything else, and their definition often shares biological, cultural, legal and emotional elements. Because of constantly evolving societies, notions of what, exactly, constitutes a family can have complex legal and emotional ramifications. Families of same-sex couples (male or female) are on the rise and as issues of homosexual rights become increasingly debated, their families are affected as well.
Modern human families are often characterized as nuclear (e.g., two parents and dependent children) or extended (e.g., parents, children, cousins, uncles, aunts, grandparents living in close proximity and engaged in regular interaction). Extended families have long been associated with many societies, and, as human lifespans have been extended and more older people are living longer, three-generation, four-generation and even five-generation families are become more common in the industrialised West as well. Under conditions of high divorce rates, and marriages later in life, single-parent families with one or more children have also become increasingly common, as have "blended" families, those with children from former relationships, half-siblings, and adopted children.