Is it obligatory for a son who received a gift from his father—consisting of a car and the outfitting of a clinic—to return a monetary amount to his siblings who did not receive the same gift, especially after the collapse of the local currency's value, and how should the value of this refunded amount be estimated?

Designating some children for a gift by the father is disliked by the majority of scholars, and prohibited by the Hanbalis, unless there is a legitimate Shariah reason such as poverty or need. A gift differs from maintenance (nafaqa), which is determined by need and custom. The father is not considered unjust or sinful by the majority of scholars, and may not be so by the Hanbalis if the gift was for a compelling reason. The son is not obligated to return the gifted money, nor is the father obligated to reclaim it according to the opinion of the majority of scholars. If restitution is due, it should be in the currency that was received, regardless of inflation, because the principle is that a right is settled with its like, not its value.