Is it obligatory for the brothers to transfer ownership of the apartment to the youngest brother based on the deceased brother's will for him to register the apartment in his name, after the deceased brother had sold the apartment to the youngest brother before his death?

It is permissible for a brother to gift some of his possessions to his brother. This gift is valid and becomes a cause for the transfer of ownership as long as the giver is fully competent to dispose of his property, provided that the recipient takes possession of this gift and seizes it. The seizure of real estate is done by vacating it and enabling control and disposal.

If the gift is valid, the apartment becomes the property of the questioner, not the rest of the heirs, and it does not enter into the deceased’s estate. Registering it in the name of the heirs without the intention of transfer of ownership does not affect his ownership.

As for the installments paid by the brothers for the apartment, if it was a donation, they have no right to reclaim it. If it was by way of exchange or the belief that they had a share, they have the right to reclaim what they paid.

Working in a usurious bank is impermissible.