When Will McGloughlin, 14, needs someone to listen to his cello practice, witness a new magic trick, or teach him to make the perfect egg salad, Grandma is his go-to person.

And when his 11-year-old sister, Reba, slumps home after a bad day in middle school, she seeks out Grandma for a heartfelt talk.

The kids don't have to go far - because Judy McGloughlin, 72, their paternal grandmother, lives right down the hall, in the bay-windowed, second-floor bedroom of their Mount Airy home.

The family - which includes parents Amy Yoder McGloughlin and Charlie McGloughlin - has lived together for a dozen years, ever since Charlie McGloughlin's father died. They were in West Philadelphia then, in a sprawling Italianate "monstrosity" (according to Amy McGloughlin) that had room for extra people.

It made sense, she and her husband figured, to open their home to his mother. Judy McGloughlin was downsizing after her husband's death; Amy and Charlie McGloughlin were busy parents, eager for an in-house babysitter. And Judy McGloughlin's contribution toward rent and utilities wouldn't hurt.

"I was on board right away," Judy McGloughlin remembers. "I'd lost my house, my husband - even my car died. But all of a sudden, I was in this whole new life. They just embraced me."

Today's multigenerational living is a timeworn arrangement with a new twist: Young adults are marrying later; older ones are living longer. The recent recession forced some families together as college graduates hunted for jobs and retirees found their savings diminished.

According to the Pew Research Center, such households are gradually growing, reversing a decades-long trend: A record 56.8 million Americans, or 18.1 percent of the total U.S. population, lived in multigenerational households in 2012, double the number who did so in 1980. And that includes only generations living under one roof - not those in side-by-side duplexes, adjacent condos, or rowhouses on the same block.

"The experiment we've had in this country with nuclear families is ending," says John L. Graham, coauthor of All in the Family: A Practical Guide to Successful Multigenerational Living. "What looks like an upswing is really a change back to the way things were."

The McGloughlins' setup requires clear boundaries, which the three adults hashed out back in the West Philadelphia house: A closed door means you knock first. When Charlie or Amy McGloughlin are home, they're the first responders to Will's or Reba's needs. And a parental "no" means "no."

Judy McGloughlin learned to navigate chaotic mornings in the family kitchen, two-stepping around her son, daughter-in-law, and grandchildren to make coffee while they grabbed lunch boxes or brushed their teeth at the kitchen sink. The children have learned to avoid heaping dirty clothes in the laundry room, so their grandmother can get to the washer.

And for all five, multigenerational living has unexpected benefits. Amy McGloughlin considers her mother-in-law a friend. Will taught his grandmother to use her cellphone. Judy McGloughlin shares family stories - including the one about the time she vaporized a roast in her brand-new microwave - with both kids.

Multigenerational living brings such intangibles, according to Graham. "There's elder-care and child-care. But more than that: There's passing along values, having a longer look at human life and understanding death."

The cultural tumble

Judy Shelton made a promise to her dying mother. Yes, she said, I will take care of Daddy.

At the time, she and her husband, Michael, were living near Manhattan; She was pregnant with their first child. Her parents lived in a small rowhouse in Philadelphia's Fox Chase section. But when her mother died, there was no question about what the family would do.

"Culturally, Chinese people take care of the elderly," Shelton says. "My father said, 'I'm not moving.' He was willing to help out with the kids. And I knew I wanted my kids to be exposed to their grandfather."

So she, her husband and baby Megan moved into the Fox Chase house. And nearly 14 years later, they are still there - her father occupying the basement bedroom, her three girls sharing a small room, and the whole family experiencing the daily tumble of cultures and generations.

Gong-gong (what Megan and her sisters, Madison and Sienna, call 81-year-old David Mark) still favors the traditional foods he buys in Chinatown: duck, for instance, and rice with every meal. The kids like pizza and noodles.

Mark calls every electronic device an "iPad." And when the girls were little, he was sometimes baffled by their parents' discipline strategies. "When Sienna was about 3, I put her in timeout," Shelton recalls. "My father could not stand it. He was hugging her."

Demographers say families such as the Sheltons, with at least one member who is an immigrant, are partly responsible for the uptick in multigenerational households. And as America becomes increasingly diverse, they expect such arrangements to rise.

The most successful ones, Graham says, will be those who talk candidly about expectations - Who will cook? Who will contribute financially? What if grandma wakes early, but her teenage granddaughter is still bopping to her iPod at midnight?

"The key," Graham says, "is balancing proximity and privacy."

For Shelton, the trade-off - a cramped space in exchange for rich relationships - is worth it. She's certain that living with family has been a boon for her father, as well. "If we didn't come to live here, I think his health would have deteriorated," she says. "I will never have the regret of not putting him in our life."

A lasting arrangement

Catherine Clever was sure her parents would kick her out of the house. How else could they respond, she worried, when they learned she was five months pregnant at the age of 15?

But for her parents, Randy and Judy Clever, who are 65 and 63, respectively, the jarring news was not cause for exile. Just the opposite: After their initial shock, they made it clear that their daughter and her child would always have a home under their Germantown roof. They still do - even though Catherine Clever is now 26 and her daughter, Maya, is 10.

For this group, weekdays are hectic - Randy Clever, retired from the city's Department of Public Health, ferries Maya to or from school, cooks dinner, and helps with homework; Catherine Clever and her mother often don't get home until after 7 p.m.

But weekends are family time: playing raucous rounds of Monopoly or Clue; cheering at Maya's soccer games; gardening, when the weather turns warm.

"They're so much fun," Judy Clever says of her daughter and granddaughter. "We have a richer life for having Catherine and Maya here."

Catherine Clever, who earned her associate's degree in behavioral science and works as a substitute and after-school teacher at Friends Select School, has come to rely on her parents' practical and moral support.

"I was hoping I'd have my own house and car by now - that I'd be a little more independent than I am," says Clever, who was adopted as a toddler. Still, this is the only home she's ever known. "We're a full family - not just me and Maya," she says. "I'm used to their help. Maybe I'll move in the neighborhood, or just across the street."

Her father laughs. "And then, we'll move in with you!"