Answer
(Fatwa: 2043/B=415/TB=1432)
Their anger and discontinuance of talking with each other is a major sin. Allah shall not accept their fardh and nafl salah, dua and any prayer due to it. If they died without reconciliation it may cause them to go to hell. This is mentioned in hadith. Instead of trying yourself, you should seek the intermediation of some influential people in this matter whom they would accept. You should also pray for their reconciliation.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband