It was going to be for just a few weeks back in 1972, when Susan and Len Lodish offered to have their brother-in-law Bob Spitz stay with them in their Wynnewood home.
Spitz was joining a start-up in the Philadelphia area, and his wife, Gloria, Susan's sister, was planning to stay behind with their young sons, both under 3, to shepherd the sale of their Ohio home.
But when it was clear that their house would not sell quickly during a market downturn, Gloria and her sons also joined her husband at the Lodish home - temporarily.
Forty-three years of togetherness later, the couples look back on a lifestyle that included rearing six boys, including the Lodishes' three and a third Spitz son.
Along the way, Susan and Gloria's then-15-year-old niece, left motherless when Susan and Gloria's sister died suddenly, also joined the household.
"This arrangement has totally worked for us. We all went into it with our eyes wide open," Gloria Spitz says. "We actually made a list of the advantages and disadvantages, and the pluses won."
Once it became clear less than a year later that the house they initially occupied in Wynnewood was too small to accommodate their two-family needs, there was a consultation with local Realtors about finding a larger home. That didn't go well.
"They didn't want to deal with us. They all thought our arrangement was weird," Susan Lodish recalls. "We got strange looks and very little help."
And then a small miracle happened: The one house in the same Wynnewood neighborhood they all had considered perfect went up for sale. The Lodish-Spitz clan bought it within a few days.
The house that became theirs is a classic three-story stone Colonial on a quiet street close to a train station, with nine bedrooms and 51/2 baths. Each couple has a master-bedroom suite and a home office.
There's a basement hangout space, complete with movie theater seats, and formal rooms in all the right places for entertaining, something the four owners do frequently.
Two kitchen renovations have yielded an ideal space for the cooking sisters: Susan's approach is precise; Gloria's, more improvisational. Despite the different styles, the sisters managed to edit a book devoted to Passover recipes called Passoverama.
A sturdy wooden kitchen table with ceramic inlays has always been command central - and has survived six hungry boys and their cousin Allison.
There's more elbow room now that both couples are empty-nesters, though the connections remain mighty. Bob Spitz, 74, vice president of a 47-member tech firm, and Len Lodish, 72, an emeritus professor of marketing at the Wharton School, clearly have a brotherly relationship that long ago dispensed with the "in-law" label.
Through the years, the couples have eaten meals and often vacationed together, belonged to the same synagogue, disciplined each other's children with full mutual consent, and amicably shared household expenses.
"It's all about communicating - and we do communicate frequently and frankly," Bob Spitz says.
Susan Lodish, 72, teaches and coaches acting and has been deeply involved in Theatre Ariel, dedicated to exploring the Jewish experience.
Gloria Spitz, 68, is the household's creative spirit, expressed through her handwork and cooking. As founder of Gloria's Kippot, she also is a pioneer in creating distinctive head coverings for Jewish girls and women.
The household goes into overdrive with Hanukkah, which begins Sunday night and commemorates the rededication of the Second Temple in Jerusalem. At the Spitz-Lodish home, it is celebrated with dinner guests, decorations, candle-lighting, and song.
Newcomers marvel at a collection of dreidels, spinning tops associated with a letter game played at the holiday. Several hundred of them, all sizes, shapes and themes, fill a handsome china closet in the large living room. They vary from the whimsical (dreidels in the shape of acorns and golf balls) to the elegant (specimens in glass and metal, often Israeli-themed).
In the front foyer, replications of Marc Chagall's magnificent windows dominate one wall, and throughout the home Judaic art and artifacts are everywhere. This is a family that delights in celebrating Judaism and its holidays and festivals.
The question often asked is: "How do you do it?" The answers are instant and emphatic.
"We feel so grateful that we've shared all of these years and so many milestones and memories," says Susan.
"But by now," says Gloria, "we just can't imagine life any other way."