1 Changing Family Structures

Family and household are not the same

Family structure describes how people are related and organized within families. Household arrangement describes who lives in the same home. These concepts overlap, but they are not identical: a household can consist of one person, relatives, partners, or unrelated roommates.

In U.S. statistics, a family household generally includes at least two people related by birth, marriage, or adoption. This statistical definition does not cover every relationship or support network that may matter in people’s lives.

A wider range of arrangements

The married couple with children remains an important family form, but it is no longer the dominant arrangement for all adults. In 1970, $67\%$ of Americans ages $25$–$49$ lived with a spouse and at least one child under $18$; by 2021, the share was $37\%$. One-person households also grew: they made up $13\%$ of U.S. households in 1960 and $29\%$ in 2023. These changes reflect shifts in family life as well as changes in the population’s age and living circumstances.

Common family and household arrangements include:

• Married-parent families, including those with biological, adopted, or stepchildren.

• Cohabiting families, in which unmarried partners live together, sometimes with children. In 2023, about $3.2$ million U.S. children lived with cohabiting parents.

• One-parent families, headed by a mother or father, and blended families, formed through repartnering or remarriage.

• Same-sex couples and families, whose visibility in official household data has increased alongside broader legal and social recognition.

• Multigenerational households, where grandparents, parents, adult children, or other relatives share a home.

• One-person and nonfamily households, including people living alone or with unrelated housemates.

• Shared or changing arrangements, such as young adults living with parents or children moving between parents’ homes.

These categories describe arrangements at a particular time. A single household snapshot may not show a child’s experience of a parent’s separation, a new partnership, or shared custody, nor does it capture every relationship and support network across a person’s life.

Demographic and economic influences

Demographic influences interact with economic and social conditions, and their effects differ across groups and generations. No single cause explains changes in family and household patterns.

People are marrying later, and more adults have never married. The median age at first marriage in 2023 was $30.2$ for men and $28.4$ for women, compared with $23.7$ and $20.5$, respectively, in 1947. Later marriage can mean more years living alone, with roommates, or with parents before forming a couple household. In 2022, more than half of adults ages $18$–$24$ lived in a parent’s home.

Lower fertility and later parenthood mean fewer households include children. In 2023, $39\%$ of U.S. families lived with their own children under $18$, down from $48\%$ in 2003. Longer life expectancy and population aging also contribute to more older adults living alone or with a spouse, and sometimes with adult children or other relatives.

Economic influences include education, employment, income, and housing costs. These can shape when people establish independent households, marry, or have children. Economic security can affect whether and when people feel ready to make long-term commitments, while high housing costs can make independent living more difficult. Family forms also vary by educational attainment and income, reflecting unequal access to stable economic resources. These factors are associated with family-formation patterns but do not determine an individual’s choices.

Social and legal influences

Changing expectations about gender roles, marriage, parenthood, and individual independence have broadened the ways people organize family life. Parenthood is less tightly linked to marriage than in earlier generations, and cohabitation has become more common.

Greater social acceptance and legal recognition have made same-sex couples and families more visible in public statistics. These changes do not mean that everyone has the same preferences or opportunities; family patterns continue to differ across communities and social groups.

Interpreting population trends

A decline in one family form does not necessarily mean that relationships or support have disappeared. Relationships may be organized across households or outside legal marriage. Likewise, the growth of single-person households reflects several circumstances, including age, partnership history, and personal choice, rather than one uniform trend.

Census figures are snapshots, and definitions or survey methods can affect comparisons. For example, federal surveys began identifying children living with two unmarried parents separately in 2007, so some earlier comparisons use a different classification. National trends describe broad patterns, not every family’s experience.