As a Muslim, one should not have such behaviour. It is one of the blameworthy characteristics- which is despised in Islam.

What you can do as a Muslim brother is to advise them not to do so. Because backbiting is a greater sin. This is based on a verse of the Qur'an which says:

"ولا يغتب بعضكم بعض "

Which means: "And do not backbite one another". (Al-Hujurat: 12)

It is your responsibility to reprimand their mistakes, in a good way, and not in a rough manner.

Whatever harm they have done to you, you have to be patient. Any harm should not be reciproated with a harm. You should always treat them well and not to hate or take revenge. Perhaps by having a good attitude and by treating them well, it is hoped that they will realize their wrongdoing hence become a better person. This is in accordance with the word of God which says:

" ولا تستوي الحسنة ولا السيئة, إدفع بالتي هي أحسن فإذا الذي بينك وبينه عداوة كأنه ولي حميم"

It means: "And the good deed and evil deed are not equal. Repel (evil that is aimed at you) in a better way; when you do so then the one who had enmity towards you, will immediately become as a close friend. " (Fussilat: 34-35)

At the same time pray that Allah keep you from any harm and may Allah give them guidance.