Cyrus (II) the Great was the King of Persia from 559-529BC. The following account is by Herodotus. He got the story by asking Harpagus' descendants, so much of it may have been altered/biased towards Harpagus. By a stroke of luck he did not die in his childhood, which I will now talk about:
Cyrus was the son of Mandane and Cambyses, and Mandane was the daughter of Astyages, King of the Medes.
The interpreters of the dreams of the Magi revealed to Astyages from a dream that Cyrus would become King instead of him. He therefore summoned Harpagus, who was a very important Mede and was the steward of all Astyages' property.
Astyages told Harpagus to kill Cyrus. Harpagus did not want to kill Cyrus because he was related to him, and because the King (Astyages) was childless, and without a male heir. So he asked one of Astyages' herdsman to do it, threatening to kill him if he did not.
The herdsman agreed but because his wife gave birth on the same day and the new-born baby died, they decided to pretend that the dead baby was Cyrus, and that Cyrus was actually their son.
When Cyrus was 13 and was playing with the village children, they made him their king in these games. He gave everyone orders, but the son of Artembares- a very powerful Mede, disobeyed and is consequently whipped by Cyrus. This boy ran off to his father who complains to Astyages.
Astyages summoned the herdsman first who revealed the truth, after being threatened with torture. He then summons Harpagus, who also confessed. Astyages hides his anger.
Astyages invited both Harpagus and his son to dinner. He cut his son up and fed his son to him. Harpagus went home and buried the remnants.
Astyages consulted the same Magi who had interpreted the dream before. They tell him that because he had already been a king unintentionally Astyages had nothing to worry about.
Because Astyages thought that there was no threat, as Cyrus had already been a king, Astyages send him to his parents, Mandane and Cambyses...