Mary-Kate Olsen and Ashley Olsen (born June 13, 1986), also known as the Olsen twins as a duo, are American fashion designers and former child actresses. The... Mary-Kate Olsen, Actress: It Takes Two. Mary-Kate Olsen (born June 13, 1986) is an American actress, fashion designer, producer, author, and businesswoman. She co-founded luxury fashion brands The Row, Elizabeth and James, and the more affordable lines Olsenboye and StyleMint alongside her identical twin sister Ashley Olsen. Olsen pursued acting independently as an adult until 2012.