Are the children obligated to repay the amount their father took from their special needs brother to complete the house construction, knowing that the father promised to repay the amount but passed away before doing so?

If a father has allocated a dwelling for one of his sons in his house, there is no blame upon him, especially if this was due to the son's need. The evidence indicates the permissibility for a father to specifically grant a gift to some of his children for a reason that necessitates such an allocation, such as need or illness.

However, after the father's death, the house becomes part of the inheritance and is to be divided among the heirs. If the father had a debt, it must be repaid from his estate before its division. If the son resided in the father's house after his death, the rent for his stay during that period can be estimated and offset against the father's debt to him. If they are equal, then there is nothing further. If the debt exceeds the rent, the heirs are obligated to repay the excess. If the rent for the dwelling is less than the debt, the son is obligated to return the surplus to the estate, unless the heirs forgive him. The forgiveness of the heirs towards the son regarding the dwelling's rent after the father's death and the son's full repayment of his debt is considered better and more profound in maintaining kinship ties.