Laws of Lashon Hara / 9: 5-6 (72)

5. One is required to prevent his children from speaking lashon hara, just like one is required to prevent them from violating any other Torah law.

6. One who tells his friend something regarding his business that seemingly he would not want him to mention to others – the listener is forbidden to pass it on. Likewise, if his friend asked him to keep it secret, the listener is forbidden to pass it on [even though it is not lashon hara] until his friend gives him explicit permission to do so.