Marin's parents met while serving in the Peace Corps. She was born in Tanzania, but her family moved to Boston when she was four months old. Two years later, her brother Mark, was born. Her father, Rodney, is a retired school teacher. Her mother , Margaret, is a judge for the Massachusetts Supreme Court. Marlin wanted to be a ballerina and studied dance until age 16 when an ankle injury ended her dancing. While concerned about her decision to pursue acting, her parents nonetheless urged her to follow her dreams. They just encouraged her to get a Masters degree so she could at least fall back on teaching. She graduated from Brown University and then transferred to New York University, where she says she was pretty terrible in her acting classes. In 1992, she met her husband, Randall, a New York theater director. After her success, they both moved to a Hollywood home that they have leased after they had a 9 month separation. Marin had her first successes performing in New York theater (Electra & The Tempest), then got some minor movie roles, and then guest roles on several tv shows before her co-starring role on "Once and Again".