Answer:
(Fatwa: 37/31/N=1433)
(1) In case the question is correct three talaqs took place on your sister and she became haram for her husband. Now she cannot marry your bahnoi (brother-in-law) without a valid halalah because talaq takes place by mobile and in the state of drunkenness.
(2) After the iddah is over the divorced woman should be married somewhere else. In this case her nikah with your bahnoi is not lawful in any way. Yes, if the second husband dies or he divorces her after having marital relations then after completing iddah she may marry her first husband.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
