بسم الله الرحمن الرحيم
If those who were present at the time when your bahnoi gave talaq, witness that he had given three talaqs in their presence to his wife or your bahnoi admits the same that he has given talaq three times to his wife then in these two cases the wife became irrevocably divorced (mughallazah bayina) and haram for her husband. The relation of husband and wife came to an end. If he wants to live again as husband and wife, they cannot do without a Shariah halalah.
فَإِن طَلَّقَهَا فَلاَ تَحِلُّ لَهُ مِن بَعْدُ حَتَّىَ تَنكِحَ زَوْجاً غَيْرَهُ [البقرة : 230]
Allah knows Best!
Darul Uloom Deoband