They r taking care of Sania(actually using her) because Adi married to her & Adi never told his parents. So they wanted to use sania to insult Kashineth in the Banaras.
ooo so banu is kashineth's brother and she(tayeeji) is his wife
No dear, kashinath pandey has a brother who I persume is dead, though he may be imprisoned and his wife is Jiji/Taiji. Kashinath has an enemy who is called Banupratab. Banu has spent 14 years in jail courtesy of Kashinath. Banu treats Jiji as a sister and vice versa.