Is your retirement plan moving in with Mom or Dad?

Darlene Chapman, 59, has just retired after nearly two decades as a Philadelphia police officer. She dreams of studying to become a lawyer, possibly a judge.

Another dream she's fulfilling? She just moved back to the home she grew up in, with her elderly father.

According to a 2015 study published in the Journal of Aging and Social Policy, the very old are the fastest-growing segment of the population in developed countries — an estimated 51 percent of elders will be 80 or older between 2010 and 2030. Typically, advanced-age children serve as primary caregivers.

Chapman looked forward to retirement with her dad. They're especially close: After her parents divorced, she ended up in foster care. Her mother remarried and left to live abroad with her new husband. By the time Chapman was 11, she had run away from foster homes, suffered abuse, and was essentially lost in the system. Her mother hadn't notified her father, so Chapman wrote him a letter.

"He found me and took me out of foster care," she said.

"She was about 11 years old when she came back to live with me," recalled Douglas Dervin, now 78.

Unlike many adult children, Chapman is not reacting to a crisis, but putting in motion a lifelong plan to share his multi-room apartment in New York City.

"We're getting used to each other," she said with a laugh. And they laid down certain rules ahead of time. "I'm not going to touch the area where he lives. I try to come and go without upsetting his schedule." She doesn't ask too many questions about his doctor's appointments, but "I'm available when he needs me."

She plans to work full-time again and go back to school. One thing was non-negotiable: She moved to his home in Harlem, rather than his moving to Philadelphia.

"I never considered moving to Philly," said Dervin. "All my grand- and great-grandkids are in Philly. But my friends are here, and so since I've retired, I find it's more comfortable to be around the people I know."

Experts agree it's best to keep your parents in familiar settings — or, if they must be moved, to arrange the furniture and keepsakes in the same way  and to stick to routines.

"I get up early, I have two choirs I belong to, so I go to rehearsals almost every day," Dervin said.

Chapman suggests adult children "be your parent's friend, do things together." Unless the living space is shared, don't meddle.

"Just ask your mom or dad how they would like this or that. Is there anything you don't want? That way, you'll know," she said.

Barry J. Jacobs, a clinical psychologist, family therapist, and director of behavioral sciences for the Crozer-Keystone Family Medicine Residency Program in Springfield, Delaware County, said it's crucial to discuss the rules ahead of time — and examine motives.

"Are you moving into your parent's house to take care of Mom or Dad? Or because you need a place to live? What is the division of space? Who uses the bathroom first, and who cooks?" he said. Also, if you as the adult child are ambivalent, "be honest with yourself. Those feelings are normal."

Sometimes, caregivers feel guilt about negative feelings. "They squash those feelings to pretend they don't exist, and put on a cheerful face. That doesn't work. Accept that you have negative feelings and figure it out from there," said Jacobs, who co-authored with Julia L. Mayer AARP Meditations for Caregivers — Practical, Emotional and Spiritual Support for You and Your Family.

"Define your values," he said: "Why are you doing what you're doing? …  People do this for a host of spiritual and financial reasons, and if you feel like you're giving back or it's morally right, that can be sustaining. If you're fulfilling a duty? That doesn't sustain caregivers very well."

What are you signing up for? Twenty-four-hour care or nights with days free? Can you have your own friends and activities? Discuss expectations before moving in, Jacobs said.

"There will be friction and conflict. Guaranteed," he said. "Will another family member mediate? What are the roles of siblings?"

Fighting over small things can really be about big things, Jacobs said. "An older person often fights old age and losing who they are by becoming controlling over small things, like moving the toaster."

But living with your parents again "can be wonderful," he said. "You can get closer than you ever have been."