The drop-off takes place on a wet winter night at a roadside coffee shop. A girl with a curtain of jet black hair sits at a table by the window, waiting, parents at her side. When headlights flash across the parking lot, she beams.

Seconds later, the door bursts open and heads turn as a grinning girl with the same curtain of dark hair walks in — an unmistakable clone of the first. She’s come with an overnight bag and a pillow. And, curiously, she’s come with two parents of her own.

“Gill!” sings the sitting family. Smiles all around as she gives the other girl an affectionate slug on the shoulder.

The four parents have driven a combined six hours through snow and rain and rush hour to meet in between their two towns. In a few minutes, one pair will turn around and head back, this time with both girls in tow.

All this so that two 12-year-olds can have a sleepover.

It’s an enormous effort for what will amount to an 18-hour visit, but it is an effort spurred by a promise made years ago, when the parents discovered their adopted daughters had a startling connection. They were identical twins.

The girls were born in China, separated by circumstance and parceled out to two different families. Whether by fortune or design — no one will ever know — the couples who adopted them were both from Ontario. And they figured it out.

Kirk and Allyson MacLeod adopted their daughter, Lily, 12 years ago and brought her home to Keswick, north of Toronto. Mike and Lynette Shaw adopted their daughter, Gillian, 12 years ago and brought her home to Amherstburg, just outside Windsor. When the parents discovered the connection, they vowed to raise them as sisters.

The situation is as rare as it is fascinating: Lily and Gillian are one of only a handful of twin pairs in the world known to be growing up in this way — apart, yet together. They are an accidental experiment, giving researchers a new window into human behavior by allowing them to study the effects of nature and nurture in real-time. For science, Lily and Gillian are a treasure.

And for the people raising them — strangers thrown together by extraordinary circumstances — the unusual arrangement has made them pioneers of a whole new kind of blended family. They are making up the rules as they go.

At their home in Keswick, Allyson and Kirk MacLeod tore open the package and stared in awe at the little girl who would soon be theirs. Tiny hands balled into fists, a sleepy gaze.

Allyson and Kirk, in their early thirties, had been trying to have a baby for years. After two miscarriages — the second at five months — they decided to adopt. More than anything, they wanted a family.

The babe in the photo wore a white dress with blue polka dots. Her cheeks were chubby, eyebrows arched in surprise, lower lip settled into a perfect pout. A patch of dark fuzzy hair, sparse in front, grew thick at the crown of her head. They named her Lily.

In a town 250 miles away, Mike and Lynette Shaw, at home with their two young children, opened their own package.

Mike and Lynette, also in their early thirties, had always wanted a house full of kids. Nearly two years before the package came, Lynette had given birth to a third child, Jonathan, who was born with a rare heart defect and died when he was only 17 days old. Another pregnancy could be difficult, both physically and emotionally. So Lynette and Mike decided to adopt.

The babe in their photo wore a pale pink sleeper with buttons up the front. She had chubby cheeks, arched brows, a perfect pout and a patch of dark fuzzy hair; sparse in front, thick at the crown. Her name would be Gillian.

The Shaws and MacLeods had met once, three months previous, at a gathering of couples adopting through the same Ottawa-based agency. They were part of a small group of parents-to-be who would travel to China together in February to pick up their children. When the photos arrived on Dec. 24, an excited e-mail exchange ensued.

But when the Shaws saw the photo of Lily, they were taken aback. Mike put the two pictures together, scanned them and sent the split-screen image back to the MacLeods with a brief message: Notice anything similar about these two?

They did. Allyson and Kirk had been thinking the same thing.

The two families contacted the adoption agency and asked coordinators to look into the matter. At first, the parents were concerned the orphanage may have inadvertently assigned one baby to two different families. Adoption documents even gave the girls the same birthday. If there were two of them, could they be twins?

Word came back from the orphanage a few days later: there were indeed two babies. Workers said the girls were found in different locations, brought in separately. They were not twins, just look-alikes.

And so the MacLeods and Shaws found themselves, two months later, at a hotel in China’s Hunan province, waiting outside an elevator with three other couples. When the doors opened, five nannies stepped out with five little girls in their arms, babies bundled into so many layers of clothing they could hardly move. Only their heads peeked out of the hooded zip-up suits they wore.

It was immediately clear to all that two of the babies were identical.

Officially, the orphanage still insisted the girls, then eight months old, were unrelated and could not be adopted together. If the parents didn’t take the baby assigned to them, they would go back into the adoption pool. And there was no guarantee they would end up together next time.

Maybe workers at the orphanage really didn’t know. Maybe they didn’t care. Or maybe, as the girls’ parents like to think, they couldn’t afford a DNA test and did what they thought was the next best thing: place the twins with families near each other.

“They could have easily sent one of the girls to Australia and one to Canada and nobody would have been the wiser,” says Kirk. “To put the girls together in the same group of people, I think the orphanage was saying to us, ‘please find out.’”

A DNA test would later confirm what the parents didn’t doubt for a moment. Lily and Gillian were twins.

Before leaving China, the Shaws and MacLeods made a pact — without having any idea what it would entail — to raise the girls as sisters. The strangers were family now.

When Nancy Segal read Allyson’s e-mail, she was floored. As a prominent twin expert and former assistant director of the renowned Minnesota Center for Twin and Adoption Research, Segal had encountered a slew of unusual multiples over the years. But identical twins being raised apart, yet as sisters? It was unheard of.

The bad news for the parents was that there weren’t any how-to manuals. The good news — for science, at least — was that tracking the twins’ growth could lead to fascinating and valuable research.

It would be difficult to overstate the importance of twins to genetic research. Twins are the vehicle through which scientists have been able to study and decode the effects of nature and nurture on our behavior, personality, and disease vulnerability.

Identical twins, who come from a single fertilized egg that splits in two, are genetic photocopies of each other. By comparing them with fraternal twins — who come from two separate eggs and are no different than non-twin siblings, genetically speaking — researchers have been able to pinpoint what is genetic and what is not.

In the late 1970s, scientists at the Minnesota Center for Twin and Adoption Research began studying what was then a new category of multiples — adopted twins who were separated at birth and reunited as adults.

Perhaps the most famous of the twins studied were Jim Springer and Jim Lewis, identicals who reconnected at age 39 and found that their parents had unknowingly given them the same name. The “Jim twins” had both married and divorced women named Linda, remarried women named Betty and had sons named James Allan and James Alan. Both had dogs named Toy.

They were an anomaly, to be sure, but a mesmerizing one that inspired Dr. Thomas Bouchard’s landmark “Minnesota Study of Identical Twins Reared Apart.” The study shook the scientific community by demonstrating, across a number of traits, that twins raised apart are as similar as twins raised together. The study’s evidence of genetic influence in traits such as personality (50 per cent heritable) and intelligence (70 per cent heritable) overturned conventional ideas about parenting and teaching.

Bouchard’s research on reared-apart twins used information that was gathered retrospectively — from the memories of twins reunited as adults and, if they were still alive, their parents. Now, twins like Lily and Gillian are giving researchers the opportunity, for the first time ever, to study reared-apart twins in real time — throughout childhood and, if all goes well, into adulthood.

Over the past decade, Segal, now a psychology professor at California State University, has found about 15 more sets of adopted twin children being raised by different families, most of them Chinese girls.

Researchers attribute this phenomenon to China’s one-child policy, which led to the abandonment of thousands of female babies. Though China’s official adoption rules state that twins should be placed together, pairs like Lily and Gillian prove things don’t always happen that way.

Twelve pairs are part of Segal’s ongoing research on reared-apart twin children, a project that promises to open a new window into human behavior. Every few years, for as long as they are willing, the twins and their parents will complete a giant questionnaire packet that tracks their behavior, attitudes, and health as they age.

Segal’s study includes a wide range of reared-apart twins. One set is growing up in the same city. Another set is separated by 5,000 miles of land and sea — one in California, the other in a tiny Norwegian village. One American family, after discovering their child had a twin, moved across the country so they could grow up together.

“The twin relationship, particularly with (identical) twins, is probably the closest of human social ties,” says Segal, who is herself a twin. This is why it’s so important for multiples to grow up together.

Segal marvels at the sacrifices parents of reared-apart twin children have made in order to nurture their bond. She has always believed strongly that twins should be raised together, but these families are the exception to her rule. “These parents have worked very hard to get these children, they are very loving families,” she says. “They immediately fall in love with these children and I think that you cannot ask them to give up a child.”

Lynette called the MacLeods and left the news on their answering machine. She knew Allyson and Kirk would want to know.

Hours later, the Shaws’ phone rang. It was Allyson. She’d heard the message just as she was about to call with news about Lily. Earlier that day, within hours of her twin, Lily had taken her own first steps.

Weeks earlier, the twins had met for the first time in Canada after spending several months apart. It was a hot day in July and the Shaws had taken a detour into Keswick on their way to Lynette’s family cottage in North Bay. The girls’ cheeks were flushed and they both wore sundresses.

When their parents sat them down on the floor, face to face, it was like plopping one in front of a mirror. The girls stared and stared at each other, puzzled and hesitant. “It was painful to watch,” says Allyson, chuckling at the memory. Many of their early visits started this way.

The parents later discovered that Lily and Gillian weren’t just identical, they were mirror-image twins: Lily is right-handed, Gillian left-handed; their hair whirls at the crown in opposite directions; both have an eyelid that droops when they’re tired, but on opposite sides. For the girls, staring at each other really was like looking in a mirror.

Growing up, Lily and Gillian were both picky eaters, both afraid of clowns and obsessed with dress-up. They loved drawing and would lie on their bellies on the floor together for hours, sketching and coloring pictures. When two-year-old Gillian started grabbing soothers from other kids and whacking them on the head, Mike and Lynette assumed the aggressive streak came from having an older brother and sister. Then Lily came to visit and they saw she had developed flying fists of her own.

Being from small towns, both families knew when they decided to adopt little girls from China that they would have a lot of explaining to do over the years. The twin thing complicated the story further.

At school one day, Gillian was asked to draw a picture of her family. In one corner of the paper, she drew herself with her parents and older siblings. Up in the top corner, in heaven, she drew Jonathan. And off to the side she drew Lily, Allyson and Kirk. The teacher thought Gillian was confused. The picture required a parental explanation.

When Lily was six, a friend questioned her about Gillian.

“Where’s your sister?” the friend asked.

“She doesn’t live with me,” Lily replied.

The friend scoffed. “Then you don’t have a sister,” she said.

Lily fired back. “My mommy has a sister and she lives in Nova Scotia and they’re still sisters.”

When the girls were little, the first thing they did when one twin arrived for a visit was run upstairs, empty the contents of the visiting twin’s suitcase and have a fashion show. They would change 15 times a day.

The clothes swap was also a tool in one of their favorite games — tricking their grandparents into believing one was the other. “WHO AM I?” they would shout, bursting into fits of laughter when Grandpa Shaw or Nanny MacLeod guessed the wrong twin.

The girls reveled in their sameness. On one visit, Lily arrived in Amherstburg with her hair cut several inches shorter than her sister’s. This upset Gillian. She pouted until Allyson took her outside and chopped her hair to Lily’s length. The girls skipped off together, new bobs bouncing at their shoulders.

The twins loved being together, which made leaving difficult for everyone. They cried and wailed and sometimes stayed gloomy for days. The separation hit Lily hardest. Without Gillian around, she was an only child again. And a lonely one. It broke her parents’ hearts. “In an odd sort of way that’s really unexplainable,” says Kirk, “there was this sense of leaving part of Lily behind when we drove out of the driveway.”

Siblings Far, a low-traffic, bare-bones weblog, is one of the few resources for families raising separated twins. It went up a few years after the MacLeods and Shaws brought Lily and Gillian home. The blog’s authors are blunt in their delivery of advice.

“This is a long-term commitment,” the site cautions. “You do not get to choose the family that has adopted your child’s sibling. It may or may not be a (compatible) match between the households.”

Jim and Susan Rittenhouse launched the website in 2004, soon after they discovered their four-year-old daughter, Meredith, had a twin.

The Rittenhouses live in the Chicago suburbs. Their daughter’s twin was adopted by a couple in Birmingham, Alabama. The twinship was discovered when Jim came across a photo of his daughter’s double on a blog. By coincidence, the girls are both named Meredith. “The story abounds in craziness. It really does,” says Jim.

In the past decade, through Siblings Far, Jim and Susan have connected with dozens of couples in similar situations. Jim says the experience with their own twin-laws has been positive, but they’ve heard from enough panicked parents to know that finding a lost sibling doesn’t always mean a happy ending. Once you’ve made the connection, they warn, you can’t go back in time. You can’t pretend not to know.

In Montreal, Anne-Marie Merkly, a 48-year-old single mom, is also raising an adopted Chinese daughter who has a faraway twin.

Flavie Merkly met her double on their seventh birthday. The twin flew in from California with her parents for their first-ever visit, a trip that was years in the making after a friend of Anne-Marie’s discovered a photo of a girl on a blog who was unquestionably a clone of her daughter.

When they met, “Flavie and her sister literally just embraced, started to giggle and then took off running,” Anne-Marie remembers. “As if nothing had happened. As if one had gone shopping and come back.”

The families spent a wonderful week together. They spoke of future visits. Flavie’s twin sobbed when it was time to leave. But months after the reunion, the other family stopped e-mailing, stopped calling, abruptly cut off nearly all communication with Flavie and her mom.

Anne-Marie has no idea what happened. “It’s very much a big question mark,” she says. “We don’t understand it.”

In the beginning, the unanswered questions drove her crazy. Was it something she said? Something they did? Truth be told, the girls live very different lives: Flavie goes to private school, her twin is home schooled. Flavie travels a lot, her twin doesn’t often leave California. Perhaps the other family disagreed with Anne-Marie’s method of parenting. She tries not to think about it anymore. There is nothing she can do.

“I think the only option that we all understood,” says Kirk, “was to say we will make the sacrifices to say this is going to work. We have to make it work.”

From the very beginning, the girls knew they were twins. And from the moment they came out of the elevator in China, the MacLeods and Shaws were family, bound by a promise to bring the girls together as often as possible. “It was like getting married all over again,” says Allyson. “All of a sudden you’re like, well, we’re hitched.”

Visits were arranged every six to eight weeks. Early on, the girls started calling each other’s parents Aunt and Uncle and acquired a shared pool of eight grandparents. “People say, well that’s a unique situation, but this is all we’ve ever known” says Kirk. “For us, it’s like a blended family.”

The arrangement works because the Shaws and MacLeods are alike where it counts — both come from large, close-knit families and have small-town roots — even though their personalities and lifestyles differ.

Over the years, the MacLeods and Shaws have spent countless holidays, weekends, and family vacations together. There are no hotel stays when they visit each other’s towns. If the MacLeods are in Amherstburg for the weekend, the Shaws give them the master bedroom. The same goes when it’s the other way around.

They give it all they’ve got, but sometimes, both couples readily admit, it’s far from perfect. “It’s not roses all the time,” Mike says. “But you have to get along, that’s just the way it is. Just like your in-laws.”

The Shaws are a busy bunch. Mike and Lynette have two other children — Heather, 17, and Eric, 16 — with jobs and commitments of their own. It’s difficult for them to get out of town, which means the MacLeods do the bulk of the traveling.

Because Lily is an only child and the MacLeods’ entire extended family is in another province, Kirk and Allyson wish the girls could get together more often. They have to remind themselves that Mike and Lynette have other children to think about. Keeping the commitment manageable for both families is one of the most difficult challenges.

Despite minor differences, the Shaws and MacLeods get along well, respect each other. So far, there have been no major disagreements. They say it’s because there is one guiding principle for all four parents: this is not about them. It’s about the girls.

With Lily and Gillian nearing their teen years, the parents acknowledge there will be challenges ahead. What happens, for example, when one twin is allowed to do something the other is not?

Already there are a few minor variations in MacLeod and Shaw household rules: Lily wears makeup; Gillian’s parents discourage it. Gillian has Facebook; Lily has to wait until she turns 13.

The girls say these differences don’t bother them much, but things are bound to change as they enter high school and bigger issues arise — parties, dating, driving.

“Can you imagine them driving the 401 to see each other?” Lynette says to Mike one day at home in Amherstburg, her eyes wide.

Looking a little further into the future, the parents wonder if the girls will go to university together someday. Kirk has his fingers crossed, though he acknowledges a lot could happen before then. “I have no idea what this relationship will morph itself into as they get older,” he says. “I just hope they stay close.”

Upstairs in Lily’s room, they swap clothes, a cute white tee for a pair of Abercrombie sweatpants. In the kitchen, they play computer games and Google things they’re curious about, like paddlefish (ew!), pink dolphins (weird!) and white tigers (cute!). For lunch, Allyson makes chicken fettuccine alfredo. It’s the girls’ favorite dish.

Four months away from their 13th birthday, Lily and Gillian say they aren’t that much alike these days. But they both play guitar and flute, both love glamour and fashion and celebrity, both have bedroom walls covered in Taylor Swift posters. They don’t wear matching outfits, but they have similar taste in clothes. Last year, they unknowingly bought each other the exact same navy blue beach cover-ups for their birthdays.

Gillian has braces now and Lily doesn’t, which makes it much easier to tell them apart. The childhood aggressive streak is gone. In the presence of strangers they have the soft, whispery voices typical of shy adolescent girls, though Lily’s is a bit softer, a bit more whispery.

Gillian tends to be more outgoing than her twin, perhaps because she is so often surrounded by siblings and cousins, aunts and uncles. “In our family,” says her older sister, Heather, “it’s pretty much if you want to be heard you have to talk loud.”

The girls can be very competitive. They compare notes on new clothes, hobbies, friends, classes. Lily says Gillian gets better grades and is more into sports. Gillian says her twin is better at drawing and guitar.

They see each other every eight weeks, give or take. They don’t cry or make a fuss anymore when they part — just a quick hug and a wave — but their families say they are quiet and withdrawn for a few days afterward.

When they’re not together, they e-mail each other every day, without fail. Gillian writes to Lily in the morning while she waits for the bus. Lily sends a note back when she gets home from school.

The girls imagine what it would be like to live together, but they don’t wish for it. “Sometimes I think about her coming to my school and what it would be like,” Lily says softly. “She might have different friends.”

Lily would like it if they lived closer to each other. “Like maybe an hour away,” she says after a thoughtful pause.

Gillian feels some sadness, knowing her twin gets lonely. “Lily misses me a lot more,” she says one day, hesitantly, when her sister isn’t around. They are both careful not to hurt the other’s feelings.

“I think if we lived together we’d be more closer,” Gillian says. “Well, we are really close now, but I think we’d be more, like . . .” She pauses to think about it. “Sisters.”

Even so, she says she feels the same kinship with Lily as she does with the siblings she has grown up with. Heather, her older sister, thinks Gillian has an even closer bond with Lily, mostly because the twins are the same age.

Together in Lily’s bedroom, the girls say that given the option between the situation they’re in and an altered past in which they end up with the same family, they wouldn’t change a thing. “Because we wouldn’t have the experience that we’ve had,” says Gillian. “Like all the stories. Memories. And then I don’t know where, like, my Mom and Dad or Aunt Allyson and Uncle Kirk would be.”

Lily agrees. “I like seeing her, but it’s cool that we get to travel and meet up at different places.” And anyway, Gillian says with a shy smile, “if we grew up normally it wouldn’t be as interesting.”

This piece originally ran in the Toronto Star. Reprinted with permission – Torstar Syndication Services.

This story is part of a two-part series on reunited identical twins. Read Part 1 HERE.