Is it obligatory for one who sits in a gathering where backbiting occurs and does not defend the honor of his Muslim brother to seek forgiveness from the one who was backbited, if he repents?

Listening to backbiting without condemnation is forbidden, and the listener is a partner to the backbiter. There is no text stating the obligation of seeking forgiveness from the one who was backbitten in the presence of the silent listener. However, many scholars have concluded that repentance from backbiting is achieved through seeking Allah's forgiveness (Istighfar) and supplicating for the one who was backbitten. Therefore, if the listener of backbiting frequently seeks Allah's forgiveness and supplicates for the one who was backbitten, that is good and will, Allah willing, clear their conscience, along with the necessity of sincere repentance to Allah Almighty for this sin.