"He quickly became the obvious choice for us and for the brand, having experience in multiple categories which we feel is essential for growth of The Row," Mary-Kate explained.
"His experience and sensibility will add great value to The Row in its next phase of development," Ashley Olsen told WWD.
The twins - who first dipped their toe in fashion waters in 2006 when The Row launched, before unveiling sister label Elizabeth & James and younger affordable label Olsenboye in subsequent years - are generally accepted in the industry as serious businesswomen following a childhood as television stars, and even found themselves in Forbes' Top 30 Under 30 list for 2011.