Do backbiting and slander أثناء الصيام invalidate the fast? And does the ruling differ if the backbiting is about a family member by another member of the same family?

Backbiting is to mention about your Muslim brother something he dislikes while it is true about him. If it is not true about him, then you have slandered him. It is forbidden by the Qur’an, the Sunnah, and scholarly consensus, and it is considered among the major sins. Allah Almighty has likened the backbiter to one who eats the flesh of his dead brother. Backbiting does not invalidate the fast, but it diminishes its reward.