You've probably heard of Rebecca Minkoff, the co-founder and head designer of the eponymous fashion brand, which reportedly pulled in more than $100 million in sales last year.

Yet the entrepreneur, whose brand sells in more than 900 wholesale stores, got an inauspicious start as an assistant to the CEO of a New York fashion company. Among her duties: Organizing the supply closet, managing shipments, and picking up the executive's son from school.

"I moved here when I was 18 to be an intern for a fashion designer," Minkoff told Inc. at a recent Startup Bootcamp Live Chat, in conversation with her brother, Uri Minkoff, who serves as CEO of the company. "My first few months, I was in the shipping department," she said. "It's hard to stomach, when you have big dreams of being a designer and you're working in the shipping department or picking up her [the designer's] son."

Still, over time, she became an expert at her more perfunctory tasks, which led the company to give her more meaningful projects to work on. "The CEO really set me up to learn and understand every aspect of the business," Minkoff recalls. "As she saw that I was excelling, she would switch me to a different department, so I really had a well-rounded view of what it was like to work at a fashion company."

Uri Minkoff also held a less-than-glamorous first job. "I was in high school, and my mother was taking care of a family friend who had been in a bad accident," he said. "I spent weekends taking care of him with a few other people. It was my first time on a team of three or four people working under me, and my first time leading."

The siblings agree that their early work experiences have shaped who they are as leaders. Both have learned to take adversity in stride, and remember that people come first.

"It was a difficult time, learning the basics of management and working with others," Uri says, though he's grateful to have seen the value of being a compassionate leader.

"All those experiences made me have the ability to say, 'I might not know this, but I'm going to learn it," said Rebecca Minkoff. "It was extremely humbling -- but so is starting your own company."