They’ve been an unmarried couple for almost 20 years. Both widowed, and now in their 90s, they maintain separate residences in Florida but mostly live together in her home — an increasingly important issue because, a few years ago, she began developing memory loss.

Sometimes she forgets to eat. She has taken some falls, too.

“His presence is helpful and supportive,” said Jenna Wells, one of her relatives and a Cornell University psychologist. “He takes her to the doctor. He takes her out to dinner.”

But he knows he will have trouble caring for her as both age and her condition deteriorates. So he proposed to her family that the two of them move together into a continuing care retirement community, where residents can shift from independent to assisted living, then to nursing and memory care units.

If they wait too long, he points out, a facility could insist that she enter memory care directly, and he won’t be able to live there with her.

The woman’s daughter, who holds her power of attorney, opposes that plan.

“She doesn’t like her mother’s gentleman friend, as we call him,” Wells said. “They’ve never gotten along. There’s mistrust about his living in her house.”

For now, with a decision on hold, the couple is managing with home care aides.

“As we see this shift, with less of a focus on marriage in older people, this is going to come up a lot,” Wells said.

That’s for sure. Eventually, most older couples will face health crises and the need for caregiving, and if they haven’t vowed their mutual marital commitment “ ’til death us do part,” their roles and responsibilities can be murky.

“We have a clear and shared understanding of what it means to be in a marriage,” said Susan Brown, a sociologist at Bowling Green State University in Ohio who studies aging and relationships. “We don’t have that kind of road map for a cohabiting or living-apart-together lifestyle.”

Yet unmarried partnerships among older Americans continue to climb. Census data from 2023 showed that of Americans ages 65 to 74, 3.9% of men and 2.6% of women, almost 1.1 million people, were living with a partner, not a spouse. Twenty years earlier, the proportions were 1.7% for men and 1% for women.

Among those 75 and older, almost 400,000 people were cohabiting, a similar numerical leap over two decades. It’s more difficult to measure the number of partners who don’t share residences, informally known as LATs (for “living apart together”), but experts believe those relationships are also on the rise.

The trend reflects Americans’ longer lives, the spike in the divorce rate in the 1960s and ’70s, and the rate of “gray divorces” occurring among those older than 50, which doubled between 1990 and 2010.

It also reflects attitudinal change. Decades ago, baby boomers led the way in cohabiting, and “for each new cohort it becomes more and more acceptable,” said Deborah Carr, a sociologist at Boston University. “The old stigma around ‘living in sin’ has pretty much disappeared.”

For older couples, “cohabiting offers many of the advantages of marrying or remarrying without the legal constraints and entanglements,” Brown said.

When partners maintain financial independence, it’s simpler for each to pass an estate along to their children. They retain eligibility for pensions or Social Security benefits that they could lose if they remarry. Remaining unmarried also protects partners from having to assume the other’s debts, particularly medical debt or the cost of long-term care.

Beyond such pragmatic concerns, cohabiting or living-apart couples “have more flexibility in defining their roles and expectations,” Brown said.

Many women, especially, “aren’t interested in the gendered bargain that marriage entails, the caregiving role,” she said.

If they have nursed husbands through terminal illnesses, “they bring a ‘been there, done that’ attitude to remarriage.”

Earlier in life, cohabiting relationships tend to be less stable and less happy, researchers have reported. But among older couples, the relationship quality is almost indistinguishable from that reported by married couples. The unions last longer than those of younger cohabitors and generally end only with one partner’s death.

What’s worrisome is that unmarried partners are less likely than spouses to have prepared advance directives, appointed health care proxies and assigned power of attorney, the process called advance care planning.

Without those decisions having been made and those documents, unmarried partners and family members can find themselves in conflict.

Older unmarried partners are also less likely to undertake estate planning. In one study, using data from the national Health and Retirement Study, Carr and her co-author, Shinae L. Choi of the University of Alabama, found that about 60% of married couples had done such planning over a six-year period. Among those who had been cohabiting, just 37% did.

“Most people don’t want to deal with this until there’s a crisis,” said Shana Siegel, an elder law attorney in northern New Jersey. Without legal authorization, she asked, “are they able to make decisions for the person they love?”

Caregiving responsibilities, too, often go unaddressed. “If he goes into a nursing home, will the house they’ve been living in have to be sold?” she said.

Same-sex partners who haven’t married tend to handle things differently, in part because they’re less likely to have children. Concerned that they’ll face discrimination or family interference, they’re more apt to do advance care planning than unmarried heterosexual couples.

Of course, any unmarried couple can take steps to provide legal safeguards.

Rik Elswit and Norma Fisher have had a committed relationship for 35 years but, in order to preserve her Social Security benefits, never married. He has no children; her daughter lives on the East Coast.

They had always kept separate residences in San Francisco. But Fisher, 86, has developed Alzheimer’s disease, which has intensified over several years, and walks with difficulty since her pelvis was fractured in a fall.

In 2022, Elswit, 79, moved into her apartment to care for her, just as she had cared for him years earlier when he faced colon cancer.

About a decade ago, “we noticed we were getting old,” he said. “We started to put the wills and the power of attorney together to be sure we were as protected as we could be.”

Siegel approves. “They have the power to help each other and make decisions as if they were husband and wife,” she said. “But if one becomes ill, the other doesn’t have the legal responsibility to foot the bill.”