Amestris

Amestris or Amastris: wife of the Persian king Xerxes, mother of king Artaxerxes I. Her reputation among Greek historians is very bad. Amestris was the daughter of Otanes, one of the seven conspirators who killed the Persian rebel king GaumÃ-ta (22 September 522 BCE). After this, Darius I the Great started his reign. According to the Greek researcher Herodotus of Halicarnassus (fifth century), Otanes was honored with a diplomatic marriage: the new king married Otanes' daughter Phaedymia, and Otanes married a sister of Darius, who gave birth to Amestris.

Link: http://www.livius.org/am-ao/amestris/amestris.htm