What is the ruling of Islamic law regarding a father's will to divide the house into two halves between the mother and the children, and to what extent does a brother have the right to claim a room in his brother's apartment, taking into account the varying contributions to marriage expenses among the children?

The inheritance must be divided according to Sharia. The wife receives one-eighth, and the remaining is for the children, with the male receiving the share of two females. A will made to an heir is not enforceable unless all heirs agree, based on the Prophet Muhammad's (peace be upon him) saying: "There is no will for an heir." However, if the heirs agree to enforce the will, such as the mother taking three rooms, then it is permissible. As for the apartment your brother lives in, if he built it with his own money or bought it, then it is his property. Otherwise, it is part of the estate, and the entire house must be divided according to Sharia. Your marrying your sister off does not waive her right to inheritance. It must be clarified whether that was a donation, a debt, or a religious obligation.