ANSWER:

You must remind them that backbiting is a major sin in Islam and leave their company until they speak of something else. As long as you have done this, you have done your duty and are not sinful in sha Allah.

Many people in family backbites a lot, beacause of which i am surrounded by backbiting environment whole day, if i ask them to stop backbite they would say its not backbiting, many times i found them backbiting when i am praying..its very difficult to avoid but i try to avoid as much as possible, am i sinful if they backbite in front of me,should i make distance with them?