There is something elegantly old fashioned about The Row’s show in New York. Old fashioned, and for that, completely contemporary. There is no scrum to get in; no photographers (runway shots are taken before anyone arrives); no A-listers; no brand encouragement to Tweet, Instagram or Vine; and every seat is a front-row seat. Models walk slowly, reminiscent of an old-school Parisian couture show, as the designer sisters Mary-Kate and Ashley Olsen sit with their audience watching their work come to life. “If people are coming to see our collection,” Ashley says later, “we want them to actually seethe collection.” The civilized set-up makes everyone feel like they are part of the in-crowd; like they have spent intimate time in the world of the Olsens: icons, power players and yet, total enigmas.

At 27, the sisters have been famous since they were both cast to play Michelle Tanner in the US sitcom Full House at just nine months old – allegedly due to neither crying when being held by a television executive. They are TV veterans, movie stars, executives of production company Dualstar, and fashion designers with over six-million internet pages dedicated to them, and yet they have never really revealed much about themselves. We have the bare facts: they are fraternal twins, born and raised in California with older brother Trent, an artist, little sister Elizabeth, an actress, and two step-siblings; Ashley is a leftie, Mary-Kate a rightie (hands, not politics); Ashley is 5ft 1in, Mary-Kate is 5ft; and they are both fascinated with fashion. Beyond that, there has been much rumored, little substantiated. It is clothing – their own labels and their style – that reveals the most.

“Anonymity is a word we talk about all the time,” says Ashley

over a green salad in New York, “in life and in clothes.” It is strange to hear two of the most recognizable faces in the world talk about blending in, but it rings true when referring to their collections. The Row (named in homage to London’s famous bespoke tailoring street, Savile Row) was borne from the hunt for the perfect T-shirt in 2006, with both girls obsessed with great fabric and fit. That criteria was then applied to a tank top, then a dress, a blazer, leather leggings and shirting – the quiet foundations of any outfit.

“We saw a space in the market,” says Ashley. “We knew there wasn’t another brand offering basics in a luxurious and contemporary way. If I wear certain designer brands, or too much of something, I look crazy, and I need something to break it up. If you are wearing a Chanel jacket and you need an anonymous piece that will show just how special that jacket is, I hope that is what The Row gives you.” They are now 23 collections on from that initial T-shirt and employ 60 people in their Manhattan atelier. And while they still offer luxury basics, the irony is that now customers want to wear The Row from top to toe and nothing else.

“We saw a space. There wasn’t another BRAND offering basics in a LUXURIOUS way”

Critically acclaimed by fashion’s toughest editors from the outset, the Olsens managed to dodge the merciless bullets so often fired at “celebrity designers” (although they claim that some people will never see them as “proper” designers). Originally the sisters wanted to have someone else pretend to be the designer, but friends reminded them that they needed to show the collection to US Vogue editor Anna Wintour. It is hard to imagine anyone selling the collection with more conviction than the twins. For they aren’t playing at fashion, they have worked with it since they were six. “[On Full House] we’d be in six-hour fittings three times a week, because we had to wear 12 different outfits,” Ashley recalls. The majority of the wardrobe was made up of adult pieces, including Chanel and Marc Jacobs, cut to fit. “We were designing clothes for ourselves as we were so petite,” Mary-Kate adds. “So I think that is when we became obsessed with fit, and now the obsession has become a profession.”

When the Olsens moved to New York from California in 2004, their personal aesthetic – named “Hobo” by the tabloids who followed them relentlessly – didn’t seem to suggest an obsession with fit. Their tiny frames were swamped in heavy knits, huge scarves, flannel shirts, pavement-dragging skirts and clumpy Balenciaga wedges. They have since said that it was simply a reaction to being cold in the East Coast weather, but the current FW13 grunge revival owes as much to them as it does to the original Seattle movement. At The Edit’s shoot, they arrive in a more refined version of that look: Mary-Kate in a black maxi teamed with a white button-down The Row shirt; Ashley in black layers enveloped in a holey scarf. (“I wear my clothes hard,” she explains.)

The name-calling paparazzi aren’t as much of a problem as they once were. “There is a threshold in New York, and once you pass that and are considered a New Yorker, they leave you alone,” says Ashley. “But we’re at the office every day, then home or out for dinner, so there aren’t the opportunities for them to take pictures. For the most part you try and avoid it… [I do], at least.”

“We were DESIGNING clothes for ourselves [as children]. We became OBSESSED with FIT”

We were NINE months old when we STARTED, so fame has always been a PART of our lives”

Mary-Kate is the more photographed of the two, but then she is perfect pap fodder – early last year she began dating Olivier Sarkozy, half brother of former French president Nicolas, 17 years her senior. Though not a subject up for discussion, the pairing makes sense after spending time in Mary-Kate’s company: the twins aren’t typical 20-somethings, nor are they typical celebrities. ‘Old souls’ seems a cliché, but there is certainly something intangible about them. They have known nothing but fame, but have used it to their advantage, never allowing it to become bigger than their plans and still maintaining their privacy for the most part. “We were nine months old when we started, so fame has always been part of our lives. There wasn’t any weirdness where we decided that we wanted to be famous,” Ashley explains. “Then as we got older, we were very fortunate that we could hire and work with amazing people who want to protect us.”

Now they are using their experience to help young people build their businesses. “I sit on a couple of boards, and [whether it is a] jewelry or furniture designer, we figure out who they need to talk to,” says Ashley. “It’s nothing for us to pick up the phone, but it means a lot to do it,” pitches in Mary-Kate. While they won’t be drawn on discussing other luxury brands, surely they must have been approached for high-profile design positions over the years? After all, they are “named” designers who have built a hugely successful luxury label. Mary-Kate answers steadily that they are just “really focused on The Row at the moment”. Ashley, however, smiles cheekily and finishes her sister’s sentence: “But we could probably help them a little…”

– Net-A-Porter