Which woman was the sister of XXX?
Otanes
The Behistun inscription has this Otanes as the son of Thukhra, in which case he could not have been the son of Pharnaspes, and so cannot have been a brother of Cassandane (who is said to have been the daughter of Pharnaspes in Histories 2.1.1, 3.2.2), and thus also could not have been brother-in-law of Cyrus II. Histories 3.68.2 and 3.70 portrays this Otanes as the first person to suspect the king of not being the son of Cyrus, and that Otanes subsequently took the initiative to overthrow him.
Cassandane