Are the apartments that a father gifted to his sons for marriage considered part of the inheritance or not, taking into account his covering the marriage expenses of his daughters, which are not counted as part of the inheritance?

If the father only housed his children in apartments without explicitly stating a gift (hibah), then the apartments are part of the inheritance. However, if he gifted them to them during his lifetime and they took possession, then they are not part of the inheritance, provided that he was just in distributing the gift between males and females; otherwise, the gift is void and must be returned. A father's spending on his daughters' marriages is considered an expenditure (nafaqah), not a gift, and does not justify preferring males in a gift.