M. Tullius Cicero Pro A. Cluentio 190

[190] She not only did not do that, but from that time forth she omitted no opportunity of planning some treachery or other, but day and night, she, a mother, directed all her thoughts to compassing the destruction of her son. But first, in order to confirm Oppianicus in his resolution of becoming the accuser of her son, she bound him to her by gifts and presents, by giving him her daughter in marriage, and by the hope of her inheritance. 67
  Therefore, among other people too, when sudden enmities have arisen between relations, we often see divorces and ruptures of connections take place; but this woman thought that no one could be sufficiently reined upon as the prosecutor of her son, unless he first married his sister. Other men, induced by new connections, often lay aside their ancient enmities; she thought that a connection with the family would be a pledge to ensure the strengthening of enmity.