A husband, wife and two children living in a single-family home.

That's the classic image of the American nuclear family.

And in New Jersey, well, it's just not true.

Only 22 percent of households in the Garden State are married couples with children under 18 years old, according to the latest U.S. Census snapshot. And the state has 6,000 fewer married-couple households than it did before the recession.

In contrast, the number of single-parent households, as well as households of people who have no familial relationship, have increased. Add in second marriages, unmarried partners and adult children living at home to save money, and you've got quite a mix.

So what's causing the change?

It's all part of a trend that began in the mid-20th Century, said James Hughes, dean emeritus of the Bloustein School of Planning and Public Policy at Rutgers University.

"In 1960, about half of all households were married families with children, the 'Leave it to Beaver' family," Hughes said.

As Baby Boomers moved out of their parents' homes, they started living alone in increasing numbers. About 12 percent of New Jersey adults now live alone, a legacy of that time period.

At that time, unmarried couples were a new phenomenon as well, Hughes said.

"Researchers had to come up with a new term to describe it: 'persons of opposite sex sharing living quarters," Hughes said.

The Census still does not collect much data on unmarried partnerships, but it does show that opposite-sex partnerships account for 5 percent of New Jersey households, an increase from 4.3 percent before the recession.

Even after marriage, today's New Jersey residents are bucking the previous century's trend with divorces and remarriages. Reports of the death of marriage have been greatly exaggerated; it's no longer true that half of all marriages end in divorce.

One expert says that, among the newest generation getting tying the knot, only about a third of marriages will end in divorce. In addition, older Americans are remarrying at a higher rate than in the 1960s, according to Pew Research Center.

About 11 percent of New Jersey residents have been married more than once.

"They like to say we don't value families as much as we used to. I joke that no, we love them so much we have two of them," Hughes said.

Millennials will probably continue to defy the traditional family mold. Many of them, burdened with student loans and unable to afford a home, are choosing to live with their parents and delay marriage and children.

"If you stuck somebody from the 60s in a time machine, who saw the world as married couples pushing strollers down the street, they would really be perplexed," Hughes said.

Erin Petenko may be reached at epetenko@njadvancemedia.com. Follow her on Twitter @EPetenko. Find NJ.com on Facebook.