Introduced toward the end of the third season, Nadia is the daughter who came along as a result of an affair between Irina Derevko and Arvin Sloane. This makes her the half-sister of Sydney Bristow and Jacqueline Sloane, the daughter of Arvin and his wife Emily. Irina's sister Katya says Nadia was born in a Soviet prison and taken away from her mother the next day.