Family life is changing. Two-parent households are on the decline in the United States as divorce, remarriage and cohabitation are on the rise. Also, families are smaller now, due to the growth of single-parent households and the drop in fertility. Not only are Americans having fewer children, but the circumstances surrounding parenthood have changed.

While in the early 1960’s babies typically arrived within a marriage, today fully four-in-ten births occur to women who are single or living with a non-marital partner. At the same time that family structures have transformed, so has the role of mothers in the workplace – and in the home. As more moms have entered the labor force, more have become breadwinners – in many cases, primary breadwinners – in their families.

As a result of these changes, there is no longer one dominant family form in the U.S. Parents today are raising their children against a backdrop of increasingly diverse and, for many, constantly evolving family forms. By contrast, in 1960, the height of the post-World War II baby boom, there was one dominant family form. At that time 73% of all children were living in a family with two married parents in their first marriage. By 1980, 61% of children were living in this type of family, and today less than half (46%) are. The declining share of children living in what is often deemed a “traditional” family has been largely supplanted by the rising shares of children living with single or cohabiting parents.

Not only has the diversity in family living arrangements increased since the early 1960’s, but so has the fluidity of the family. Non-marital cohabitation and divorce, along with the prevalence of remarriage and (non-marital) re-coupling in the U.S., make for family structures that in many cases continue to evolve throughout a child’s life. While in the past a child born to a married couple – as most children were – was very likely to grow up in a home with two parents, this is much less common today, as a child’s living arrangement changes with each adjustment in the relationship status of their parents. For example, one study found that over a three-year period, about three-in-ten (31%) children younger than 6 had experienced a major change in their family or household structure, in the form of parental divorce, separation, marriage, cohabitation or death.

The growing complexity and diversity of families

The share of children living in a two-parent household is at the lowest point in more than half a century: 69% are in this type of family arrangement today, compared with 73% in 2000 and 87% in 1960. And even children living with two parents are more likely to be experiencing a variety of family arrangements due to increases in divorce, remarriage and cohabitation. Today, fully 62% of children live with two married parents – an all-time low. Some 15% are living with parents in a remarriage and 7% are living with parents who are cohabiting. Conversely, the share of children living with one parent stands at 26%, up from 22% in 2000 and just 9% in 1960.

These changes have been driven in part by the fact that Americans today are exiting marriage at higher rates than in the past. Now, about two-thirds (67%) of people younger than 50 who had ever married are still in their first marriage. In comparison, that share was 83% in 1960. And while among men about 76% of first marriages that began in the late 1980’s were still intact 10 years later, fully 88% of marriages that began in the late 1950’s lasted as long, according to analyses of Census Bureau data.

The rise of single-parent families, and changes in two-parent families

Despite the decline over the past half century in children residing with two parents, a majority of kids are still growing up in this type of living arrangement. However, less than half—46%—are living with two parents who are both in their first marriage. This share is down from 61% in 1980 and 73% in 1960.

An additional 15% of children are living with two parents, at least one of whom has been married before. This share has remained relatively stable for decades.

In the remainder of two-parent families, the parents are cohabiting but are not married. Today 7% of children are living with cohabiting parents; however a far larger share will experience this kind of living arrangement at some point during their childhood. For instance, estimates suggest that about 39% of children will have had a mother in a cohabiting relationship by the time they turn 12; and by the time they turn 16, almost half (46%) will have experience a household where their mother has cohabited. In some cases, this will happen because a never-married mother enters into a cohabiting relationship; in other cases, a mother may enter into a cohabiting relationship after a marital breakup.

The decline in children living in two-parent families has been offset by an almost threefold increase in those living with just one parent—typically the mother. Fully one-fourth (26%) of children younger than age 18 are now living with a single parent, up from just 9% in 1960 and 22% in 2000. The share of children living without either parent stands at 5%; most of these children are being raised by grandparents.

Blended families

According to the most recent census data, 16% of children are living in what the Census Bureau terms “blended families” – a household with a stepparent, step-sibling or half-sibling. This share has remained stable since the early 1990’s, when reliable data first became available. At that time 15% of kids lived in blended family households. All told, about 8% are living with a stepparent, and 12% are living with step-siblings or half-siblings

Many, but not all, remarriages involve blended families. According to data from the National Center for Health Statistics, six-in-ten (63%) women in remarriages are in blended families, and about half of these remarriages involve stepchildren who live with the remarried couple.

Births to unmarried women

In 1960, just 5% of all births occurred outside of marriage. By 1970, this share had doubled to 11%, and by 2000 fully one-third of births occurred to unmarried women. Non-marital births continued to rise until the mid-2000s, when the share of births to unmarried women stabilized at around 40%.

Multi-partner fertility

Related to non-marital births is what researchers call “multi-partner fertility.” This measure reflects the share of people who have had biological children with more than one partner, either within or outside of marriage. The increase in divorces, separations, remarriages and serial cohabitation has likely contributed to an increase in multi-partner fertility. Estimates vary, given data limitations, but analysis of longitudinal data indicates that almost 20% of women near the end of their childbearing years have had children by more than one partner, as have about three-in-ten (28%) of those with two or more children.

Same-Sex Parents: A Statistical Snapshot

The U.S. Census Bureau’s 2013 American Community Survey was the first to collect detailed demographic data on both married and unmarried same-sex couples nationally, including information on same-sex couples raising children. The Williams Institute on Sexual Orientation and Gender Identity Law and Public Policy at the UCLA School of Law analyzed that data, along with information from the 2013 National Health Interview Survey. The institute estimates that, as of 2013:

• Nearly 210,000 children under the age of 18—almost 145,000 of them school-age—lived in some 122,000 households with same-sex parents.
• A third of those children were being raised by married same-sex couples, and that proportion was even higher—just over half—in the District of Columbia and states that allowed same-sex marriage in 2013.
• Female same-sex couples accounted for more than three-quarters of such couples raising children.
• Same-sex couples were almost three times as likely as different-sex couples to be raising adopted or foster children.
• Racial or ethnic minorities accounted for more than a third of same-sex couples raising children.
• Those in same-sex couples raising children were about three years younger on average—38.6 years old—than individuals in different-sex couples raising children.
• Nearly a quarter of children being raised by same-sex couples were living in poverty.
• However, fewer than one in 10 of the children in married same-sex households were living in poverty. And married same-sex couples with children had significantly higher annual median household incomes than same-sex couples who were unmarried—$97,000 vs. $75,000—along with higher rates of home ownership.