Even after Myrtle Lewis’s mother reached her late 90s and could no longer drive or care for herself, she insisted on remaining in her home in Northeast Washington. Lewis, who was helping care for her mother, arranged for her to have a live-in companion, another older woman, named Kizzie. But watching her mother’s world shrink as she knocked around a too-big house clarified a few things for Lewis, now 76.

“After a while it just became she and Kizzie. They’d go to bed at 6:30,” she said.

Unlike her mother, who stayed in her house until three months before she died at 98, Lewis is open to someday selling or renting out her house and moving to a senior facility. “I want more companionship,” she said, “multi-age companionship in a group, and people who share some interests, and stay as involved as I can in growth and development and health.”

AARP estimates about 41 million Americans care for their adult family members, a number that has increased as life expectancy has grown. About 4 in 10 such caregivers say they have plans in place for their own future care, according to the organization’s 2015 Caregiving in the U.S. survey.

Often, people who are relatively young and healthy don’t spend much time contemplating what life will look like when they get old and frail — until they see it reflected in the life of a loved one.

“No one wants to think about their own aging. Everybody puts it off,” said Amy Goyer, a family and caregiving expert at AARP. “With our parents living longer, we are getting more involved in it as an ongoing situation. Our parents’ parents didn’t live as long, but for baby boomers it gets harder to ignore — it’s a repeated smack in the face of reality.”

Seeing a parent’s body or mind break down can inform decisions about one’s own old age, from the practical — finding a house on a single level, installing grab bars, touring living facilities — to the philosophical, such as learning empathy, shoring up social ties or accepting one’s own limitations.

For Richard Lui, 52, an MSNBC news anchor in New York City, becoming a caregiver for his father, who has dementia, forced him to grow emotionally. After his father, a retired pastor in San Francisco, began to have memory problems eight years ago, Lui started flying there each week to help care for him, as his father gradually lost his ability to communicate.

The experience, while wrenching, also resulted in a breakthrough. Seeing his once independent father so vulnerable felt like holding up a mirror on Lui’s own potential frailty. He also began to think more about financial planning and long-term-care insurance. “Eight years ago I thought I was forever young. But no, I’m not, and I need to think about that for my own health and personally,” he said. “I have to run toward the fire. I have to. I can’t run away from it.

Now when people ask how he is, Lui is more willing to share the hardships. “I will try to answer as honestly as possible,” he said. He also serves as a caregiving “ambassador” for AARP; the Alzheimer’s Association; Embracing Carers, a caregiver advocacy group; and BrightFocus Foundation, which supports research on Alzheimer’s and vision diseases.

Such clearheadedness is typical of people caring for family members, said Denise Brown, a Chicago-based caregiving coach who started CareGiving.com in 1996. “When you’re a family caregiver, you’re not in denial about death and aging and what happens when we get older,” she said. “We know that we’re not going to live forever — we live it. It’s not necessarily immediate for most people, but we live it.”

Brown started caring for her parents in 2004 and made a vow to herself when, after a medical crisis, her mother was unable to return from a rehabilitation facility to her house. “It was awful to tell her she couldn’t go home,” she said. “I want to make sure I’m set . . . where I don’t have to rely on other people to pack up my house and move for me.”

To forestall this, Brown, 56, has identified a continuing-care facility she is considering for her next move: “It’s beautiful. It’s got a campus. I feel like when I’m 70 I’ll have enough energy for the move and then I’ll have enough energy after the move to enjoy it.”

It wasn’t until he became his mother’s full-time caregiver that Dave DiBella, 71, of Pittsburgh realized how unprepared he was for his own aging. When she fell and injured her hip 10 years ago, he retired early from his job as alumni and gallery director at the Art Institute of Pittsburgh and moved in with her.

“That was a year of being tested beyond anything I could have ever imagined,” he said. “It made me so afraid that I’ll be dependent on somebody.”

To stave that off, DiBella said, he is consciously staying fit. He is also taking more seriously the idea of organizing his affairs, such as writing a will and designating beneficiaries. “I was a bit of an ostrich before,” he said. “Now I realize that I’m not the exception to the rule.”

Dale Brown, 65, a retired federal policy administrator in the District who helped care for her parents, is shopping for a condo that, unlike her current one, is all on one level, with an elevator and wheelchair accessibility.

“Once I get it, I’m going to set it up for the 95-year-old Dale,” she said. “I’m going to get lever door handles. I’m going to try to get a walk-in tub, and a room where I can put someone if I need help.”

Caring for a parent can also crystallize what a person doesn’t want. Jeffrey Slavin, 64, the mayor of Somerset, Md., and his sister have been decluttering their 94-year-old mother’s house as they care for her, secretly slipping out with books and other items.

That has convinced Slavin to start getting rid of his own possessions, including art and some pocket watches from a collection his father left him. “I’m giving away things now that I want people to enjoy in my lifetime,” he said.

Lewis, too, is taking steps now to forge a path different from her mother’s. Seeing her mom give up driving prompted her to get cataract surgery to maximize her years behind the wheel. “I’m trying to hold on as long as I can,” she said.

Some have a more radical take. Seeing her parents grow old and frail made Holly Tippett think she might consider ending her life rather than become incapacitated. Tippett, 57, a fundraiser for a nonprofit group in the District, helped care for her father as he was dying and was her mother’s primary caregiver for a year.

“It makes me realize that I don’t want to get super old and I don’t want to be a burden on my children,” she said. “I don’t think the quality of life is worth the burden on family and friends.” Recalling seeing her father, a successful business executive, reduced to incontinence, she said, “I don’t want to live like that, and I don’t want my kids to see me like that.”

For Roberta Youmans, 65, a retired Department of Housing and Urban Development employee in the District, caring for her mother, who had Parkinson’s disease with dementia, made her “a little more worried about aging than I think some of my friends are.”

Because of this, she signed up for Medicare B even though she already has a government pension, and she thinks twice before spending money on things such as travel. She also learned to appreciate small victories: “I spend a lot more time being grateful for what I can do. ‘Oh my God, my legs are still okay,’ having seen my mom not be able to walk. I can still smell. I can still see.”

“Little gifts, like, ‘Oh, she matched up two buttons, that’s great,’ when she used to do 5,000-piece puzzles,” she said. “I really learned a lot about life, death, aging, and what’s important.”