Must the sisters wait for their two brothers to complete building the apartment building in order to benefit from it, or are they entitled to demand their share of the house agreed upon before their father's death?

It is permissible for a person to divide his wealth during his lifetime, provided that he does not intend to harm the heirs, and the division is for the male like the share of two females. If the wealth is given ownership to each heir, this is a gift that requires justice. If ownership is not given, then it is a will that is not permissible for an heir unless approved by the heirs after death. If there is mutual consent to a preferential division with explicit consent not based on shyness, then it is permissible. However, if the consent is not wholeheartedly given, then the division must be re-done according to Islamic law, because Allah has undertaken the division of inheritance.