In many ways, the life that Karen Kanter and Stan Tobin share in Philadelphia sounds entirely typical. Both 75, they see movies and plays together, visit children and grandchildren, try new restaurants (but avoid sushi).

Tobin, an accountant who maintains a small tax practice, attends a monthly men’s group. A retired middle-school teacher, Kanter hustles between book and art appreciation groups while volunteering and writing a historical novel.

He supported her through a successful breast cancer treatment years ago. She has been prodding him about putting on pounds, so he has returned to Weight Watchers. Careful about financial and legal arrangements, she has his power of attorney and health care proxy, and vice versa.

“We love each other and want to be together, and we’ve made the commitment to stay together until death parts us,” Kanter said.

But although they have been a couple since 2002 and have shared a home since 2004, they are not married. And among older adults, they have a lot of company.

The number of people over 50 who cohabit with an unmarried partner jumped 75 percent from 2007 to 2016, the Pew Research Center reported last month — the highest increase in any age group.

“It was a striking finding,” said Renee Stepler, a Pew research analyst. “We often think of cohabiters as being young.”

Most still are. But the number of them over 50 rose to 4 million from 2.3 million over the decade, Stepler found, and the number over 65 doubled to about 900,000.

A rise in ‘gray divorce’

The trend partly reflects the sheer size of the baby boomer generation, as well as its rising divorce rate. So-called gray divorce has roughly doubled among those 50-plus since the 1990s.

“People who’ve divorced have a more expansive view of what relationships are like,” said Deborah Carr, a sociologist at Rutgers University in New Brunswick, N.J. “The whole idea of marriage as the ideal starts to fade, and personal happiness becomes more important.”

Both Kanter and Tobin are divorced after decades in their respective marriages, and they cite their failed unions as a reason they don’t want to start another one.

“Getting divorced gives you so much to untangle,” Kanter said. “Our life is good together, so why disturb it?”

Tobin agreed: “The relationship is looser. We don’t make demands on each other’s time. She has her life; I have my life, and we have our life together.”

It’s a boomer thing

The baby boomers pretty much invented premarital cohabitation while in their 20s and 30s — or like to think they did.

“It used to be called shacking up, and it was not approved of,” said Kelly Raley, a sociologist at the University of Texas, Austin, and former editor of the Journal of Marriage and Family.

Religious groups often condemned living together outside marriage then, but the general public is far more accepting now, she said, and people turning 60 today “are very different” from the 60-year-olds of the past.

Demographers see most youthful cohabitation as a prelude to marriage or simply a short-term arrangement. In later life, however, cohabitation — like remarriage — brings companionship and wider social circles, not to mention sexual intimacy, at ages when people might otherwise face isolation.

Financial concerns

Not getting married also enables the cohabiters to take advantage of the cash-flow benefits of pooling their resources without making them vulnerable to their partner’s financial obligations.

“You become responsible for your legal spouse’s debt, but not for your cohabiting partner’s debt,” Carr said.

Marrying also can affect government and pension benefits.

Consider Jane Carney and Norm Stoner, who live in Oklahoma City and were both widowed. For years, even after he moved into her house in 2004, they debated whether to make their union legal.

“The list of pros was very short, and the list of cons was very long,” said Carney, 69.

Among the latter: Each was receiving Social Security survivors benefits, checks that would have stopped had they remarried. Nor will one partner’s assets prevent the other from qualifying for Medicaid.

Even if an older couple don’t want to sign a marriage certificate, some legal steps should be taken, lawyers say. Documenting end-of-life wishes, designating health care decisionmakers and writing wills are even more important than for married couples, for whom laws cover such situations.

Without the necessary paperwork, cohabiters could find themselves being shut out of the process by children or other relatives.