We live and work together, so initially when we started the business, it was intense," says Nicole Kunz, one half of the handsome brother–and–sister team at the sportswear label Nicholas K. "We hadn't been under the same roof together in so long, and you kind of revert to childhood," she explains, suggesting a home/office setup reminiscent of the late Arrested Development.

Sibling strife and claustrophobic family life aside, in the past four years the pair have settled nicely into their respective roles, with Nicole designing travel–ready separates for men and women in muted cottons, linens, and wools while Chris oversees production, distribution, and marketing. The whole enterprise is packed inside a loft space in Manhattan's Chelsea neighborhood, and their routine goes something like this: Nicole conceives the clothes, keeping in mind Chris—an avid hunter, fisherman, and hiker. Big brother then watches over a factory near Shanghai—built specifically for Nicholas K—and personally checks zippers and cuffs on each piece before it ships to, say, a friend's shop or Bloomingdale's. "It helps to have someone who doesn't have a fashion background," notes Chris, meaning himself. "When you wear clothes in the outdoors, you really think about function. You don't want a seam to tear or a button to break."

The Kunzes grew up as nature–loving children in Tucson, with a Chinese–Russian mother and German–Irish father, which made for a striking genetic brew. Before starting Nicholas K, Chris modeled and Nicole worked in design at DKNY, Coach, and Nautica. "I just hit a turning point in my career, where I didn't see myself going down that path," says Nicole, much preferring to be in charge. She adds, "I work weekends, I work nights, I work crazy hours. But when I leave, I want to leave"—right before Chris jets off to stalk elk in the Arizona wilds.