What exactly the word “family” refers to is among the more contentious issues in American society. Religious conservatives, on one hand, point to an understanding of the ideal “nuclear family” that they claim has existed from the beginning of society - epitomized in Adam & Eve and their children. By contrast, progressives contend that many non-traditional families (grandparents, siblings, or other family members serving as guardians; one-parent families due to death, divorce, adoption, or pre-marital sex; blended families with two parent systems due to divorce/remarriage) have existed for a long time, but simply have been widely unrecognized by conservatives.
Today, the family is understood with much greater complexity and controversy than ever before. The non-nuclear family, along with same-gendered married couples, now are challenging notions of what constitutes a family (and marriage). While progressives/liberals tend to celebrate the expanding understanding of the family structure, many conservatives are troubled at the ways traditional family values they cherish are sometimes viewed as antiquated, unimportant, or exclusionary.
“What and who” is family is the primary issue - as well as who/what defines? (Bible, each person, civil law)
On these questions, the nation (and world) have engaged in an intense fight that, depending on accounts - has either been settled or will continue indefinitely.