What is the ruling on a father writing the fourth apartment for females, knowing that the males built the other three apartments?

A father must be just among his children in giving gifts, and preferring some over others without a justifiable reason of need or poverty is an injustice for which he incurs sin. If a father singles out some of his children for a gift or prefers them without cause, then along with repentance, he must return what was given preferentially to some or give the others what completes their share.

If a father gifts the air rights (the rooftop) to his children, then what they build on it does not enter into the inheritance and becomes their property, provided that he has gifted the equivalent of that gift to the rest of his children. However, if he permitted them to build without a gift, then it is a loan (عارية) that ends with the father's death, and the floors will belong to the heirs, while his children who built the floors will have the value of the construction.

And if a father singled out his children with the gift of the rooftop and did not gift anything to the rest of his children, then this is a void gift that is returned after death, and what they built will not be their property; rather, they will have its value.