What is the Sharia ruling on children seizing residential apartments in a house built with the agreement that it would be for all family members, and what is the ruling on the father accepting his eldest daughter's contribution and her taking possession of it, and what is the ruling on the fourth son accepting a room on the first floor, and should he keep it, return it to the father, or give it to the eldest sister?

The agreement reached between the father, his son, and his daughter to jointly build the house is invalid due to ambiguity (jahalah) and uncertainty (gharar), as the amount of capital contributed by the father to the construction of the house is unknown. The certainty of capital in a partnership is a condition for its validity, by agreement of jurists. If the partnership is invalid, then the first two floors belong to the elder son and the elder daughter. They must estimate what their father spent on them and return it to him. As for the third floor, it belongs to the second and third sons.

If the daughter gifts her share to her father, she is permitted to do so. The father may dispose of what was gifted to him, after taking possession of it, as he pleases within the bounds of lawful disposition. However, he is obligated to be just among his children in gifting.

As for the land, each of the father, son, and daughter has ownership proportional to what they paid. Accordingly, the father has a claim against his children for his share of the fair market value for the airspace above the land, and likewise, the elder children have a claim against their siblings. It is advisable for the father and his children to reach an understanding. If an understanding cannot be reached, the matter should be referred to the judiciary.