Mary-Kate Olsen has Norwegian, English, German, 1/8th Italian, and distant French ancestry.
Mary-Kate Olsen was born on June 13, 1986, in Sherman Oaks, California, the United States, to Jarnette "Jarnie" Olsen and David "Dave" Olsen. While her mother was a personal manager, her father worked as a real estate developer and mortgage banker. She has a twin sister, Ashley, an older brother Trent, and a younger sister Elizabeth Olsen.
She also has an elder brother named Trent Olsen and a younger sister named Elizabeth Olsen. Elizabeth also went on to become an actress. Her parents got divorced in 1996 and her father later remarried. She has two younger half-siblings, Taylor and Jake, from their father's second marriage.