Answer: All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.

In principle, a buyer who purchases an item and takes on its liability is allowed to sell it at any price they choose. However, this provided that the item is not mortgaged. Moreover, there is no connection between the first contract and the second contract.

In light of the situation described in the above question, the relationship between the bank's client (the father) and his paternal aunt`s children who bought the apartment from him is that of a seller and buyer. There is no connection between the contract made between the bank and its client and the contract between that client and his paternal aunt`s children. If the bank waives the client's installments due to his death, it does not waive the debt owed by his paternal aunt`s children who bought the apartment from him. This is stated in the Iftaa` Council`s Resolution No. (251) (2/2018). In addition, it is stated in [Hashiyat al-Shirbini 'ala al-Ghurar al-Bahiyya, Vol. 3/P. 21]: "If the price reduction occurs after the Murabaha sale has become binding, it does not extend to the second buyer." Similarly, in [Al-Bayan fi Madhhab al-Imam al-Shafi'I, Vol. 5/P. 335]: "Even if the first buyer sold the item verbally and then the price is reduced for the first buyer, this reduction does not apply to the second buyer."

In conclusion, the second buyer (Children of the first buyer`s paternal aunt) isn`t exempted from the debt because the first buyer was exempted from it. And Allah the Almighty knows best.