How is the estate of a man to be divided who died leaving a mother, two sons, and two daughters, knowing that one of the sons built an additional floor on the house left by the father before his death, then he himself died, and after the death of the father and the first son, the second son converted the ground-floor shops into an apartment and finished the upper floor that his deceased brother had built?

The mother's share of the inheritance is one-sixth. The remainder is to be divided among the two sons and two daughters, with the male receiving the equivalent of two females' shares. Thus, the inheritance is divided into 36 shares: the mother receives 6 shares, each son receives 10 shares, and each daughter receives 5 shares. The share of the deceased son passes to his heirs.

As for the floor built by one of the sons, there are two scenarios: 1. If he built it with the consent of the heirs: The construction is considered a loan (ariyah). If the agreed-upon or customary period ends, the apartment is appraised, either dismantled or standing, and its value is paid to the son who built it. Then, the apartment becomes the property of all the heirs. If the building son dies before the period ends, scholars differ: Hanafis, Shafi'is, and Hanbalis: The loan contract is nullified by the death of the borrower, and his right is personal, not transferring to his heirs. Malikis: The right of usufruct transfers to his heirs for the remaining period, unless the lender stipulated that only the builder himself could benefit. 2. If he built it without the consent of the heirs: It is considered an act of usurpation (ghasb), and it takes the ruling of what a partner builds on shared land without the consent of the other partners.

As for the second son's finishing of the apartment and converting the shops into an apartment: If it was with the permission of the heirs and those who have the right of usufruct, then there is no harm, and it is considered a loan (ariyah). Otherwise, he is a usurper.

In case of disagreement, the matter must be referred to the Sharia court or to knowledgeable scholars.