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Photo: Tommy Lucas/Sweden Unlimited

You often hear designers say that their biggest style influence is their mother or grandmother. But in the case of brother-sister duo Chris and Meggie Kempner, the adage is especially apt. Their grandmother, socialite/philanthropist Nan Kempner, was an original flavor street style icon and couture connoisseur, whose photo regularly appeared in newspapers and fashion magazines around the world throughout the 1970s, '80s and '90s.

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Photo: Tommy Lucas/Sweden Unlimited

One of Yves Saint Laurent's best friends—and best customers—Nan Kempner (who was also said to have inspired the phrase "social X-ray" in Tom Wolfe's novel Bonfire of the Vanities) was renowned for her effortlessly elegant inclinations. In fact, her wardrobe was so legendary that it was displayed at the Metropolitan Museum of Art Costume Institute in a 2006 exhibit titled "Nan Kempner: American Chic" (Kempner died in 2005 at the age of 74.) As Diana Vreeland famously said of the nightlife-loving fashion plate, who was as comfortable at a black-tie ball in Paris as she was on the Studio 54 dance floor: "There is no such thing as a chic American woman. The one exception is Nan Kempner."

Related: The Darker Side of Yves Saint Laurent

So it's no wonder that Chris (who just completed his MBA at Harvard Business School) and Meggie (a former stylist at Ralph Lauren) were inspired by the woman they called "Grand Nan" for their newly launched label, Kempner.

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Photo: Tommy Lucas/Sweden Unlimited

"I remember being on vacation with my grandmother in the Bahamas when I was younger and sitting with her while she unpacked—this took a while [as] she did not travel lightly," said Meggie (who studied at Parsons and attended her first runway show with Nan at age 12). "I noticed this pair of Gucci by Tom Ford beaded and feathered jeans. They were the coolest things I'd ever seen. I was instantly hooked on fashion and began working towards building my career. I knew one day I would design my own collection."

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Photo: Tommy Lucas/Sweden Unlimited

Related: 10 New Designers to Watch at NYFW

"The idea has always been that we wanted to be in the business of 'manufacturing cool,' making women feeling as confident as we could," added Chris of the Kempner collection, which is designed and produced in New York City. "We realized that we could do this by combining our backgrounds in fashion and investing, while simultaneously subtly paying homage to our grandmother and doing something that we hope she would have been very proud of."

The result is a line of sophisticated-meets-edgy separates meant to showcase the wearer's own unique sense of style (Nan eschewed head-to-toe runway looks, preferring to cherry-pick the best pieces from different designers each season and put them together with her own personal spin). To this end, Kempner's fall 2014 debut offers a tightly edited selection of mink-trimmed or abstract floral print suits (Nan was one of the first women to embrace the '70s menswear trend), a black blazer with slim leather lapels, a color-blocked lattice pullover in navy and forest green piped in autumnal orange, easy, chic day dresses and a smattering of beautifully cut outerwear with bold metal buttons (a nod, perhaps, to YSL's classic wool coats). All the pieces look great worn together—as seen in the Kempner look book and video shot in Nan's Upper East Side Park Avenue apartment—but would look equally swell paired with existing pieces in any woman's closet.

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Photo: Tommy Lucas/Sweden Unlimited

For spring 2015—which will be unveiled at their first-ever New York Fashion Week presentation at The Glass Houses in Chelsea this week—the siblings plan to incorporate lingerie elements and pops of neon python to heighten the boy-meets-girl sensuality of the collection, which retails from $295 to $3,600 at FiveStory and Moda Operandi.

As for what separates Grand Nan's style from that of current street style stars, who tend toward more photo-ready, over-the-top ensembles?

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Nan's style was very polished and chic, but always had a creative flair," said Meggie. "She rarely bought head-to-toe looks, because she had so much fun styling looks her own way. She was so great at putting separates together in cool, unexpected, and daring ways. Dressing in separates, like Nan did, is how the new generation dresses, me included. She was tying her button downs up above her belly button before the crop top was cool!"

They say that imitation is the sincerest form of flattery. In the case of Kempner, it's also a sartorial love song to one incredibly chic grandma.

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Photo: Tommy Lucas/Sweden Unlimited