Midrasch zu Esther 9:14

Rabbi Eliezer said: Haman had forty sons; ten of them were the scribes of the books of the king, and thirty were ruling in all the provinces, as it is said, "And the ten sons of Haman, in the rest of the king's provinces" (Esth. 9:12). They were all hanged upon the gallows of their father, as it is said, "And they hanged Haman's ten sons" (Esth. 9:14) upon the gallows. Another Scripture text says, "And they hanged Haman's ten sons" (ibid.).