Good things do come in pairs

 NEW YORK — “There is a certain amount of face time that you need when you have a brand,” Ashley Olsen said. “We just wanted to function more behind the scenes.”

 It was a sultry afternoon in August, and Olsen and her sister Mary-Kate were visiting the production office of The Row, their two-year-old fashion label, on West 39th Street. The Olsens, despite being very rich women, have clearly chosen not to spend money on decor. The furniture is nicked, the windows mossy with grime, and the five employees who share the two-room office have to step around a stack of fabric bolts.

 At least a tropical plant on one of the desks offered a bright spot of vitality.

 “It’s fake,” Ashley said.

 Her sister, the dreamier of the two, looked at the artificial greenery and said in a tone of rising lightness, “The table fell over the other day and the pot didn’t break and I was so mortified and impressed.”

 This seems to be the classic response to the Olsen sisters as well. To read blogs devoted to them is to feel a queasiness with the fact of the Olsens — their physical smallness (“the magical millionaire pixies,” as one site refers to them) and, of course, their wayward style (“bad breath and dirty hair,” to quote another). Very few celebrities are either so fascinating or appalling that they manage to get under our skins, as Mary-Kate and Ashley Olsen have, and it may be because they are twins. Yet their success in a field as competitive as fashion is impossible to deny. The Olsens, who are 23, have succeeded with two different labels simultaneously — The Row and the hip, less expensive Elizabeth and James — and without formal design training.

 Elizabeth and James (named for two Olsen siblings) is produced under a license with L’Koral Industries, a denim and contemporary sportswear maker, and is sold in 300 stores, according to its president, Jane Siskin. The brand expects to double its apparel sales this year.

 The Row is really Ashley’s brainchild, though the sisters share responsibilities. Nearly four years ago, while a student at New York University and ducking the paparazzi hired to follow her and her sister everywhere, Ashley gave herself the goal of creating, in her eyes, the perfect T-shirt. That was the concept behind The Row: beautiful but practical clothes whose fit and luxurious texture (T-shirts in sheer cashmere, leggings in stretch leather) had private meaning to the people who wore them.

 Most good designers are mad for fit, and true-blue fashion consumers make choices on that basis, but the Olsens saw fit as a kind of ruthlessly modern sensibility. Their chaste black blazer, for example, has a high armhole because the Olsens liked the way Paris couture jackets fit, with high armholes and narrow sleeves that make your arms look even skinnier and longer. Being small, about 152 centimeters tall, they have always had a thing about proportion.

And though Ashley, the alpha sister, came to the meeting in the production office dressed in a plaid cashmere shirt from The Row’s fall line and a black miniskirt, the label can’t be said to reflect the Olsens’ wildly random style — sometimes, perhaps uncharitably, called Dumpster chic. Mary-Kate, her eyebrows bleached, had on a vintage black leather skirt with a long-sleeve print T-shirt that she last wore, she said, about eight years ago.

 “The majority of our customers are 35 to 60,” Ashley said. “Yeah, I wear a lot of stuff because it’s basic. It’s that ageless design that we try to focus on, but it’s not defined by one of us.”