Is it permissible, in Sharia, for one of the siblings to purchase an additional area from the share of another sibling in a plot of land that was won through a governmental lottery, prior to the completion of construction and the payment of the full price?

If the government stipulates in the contract for the purchase of a plot of land that its ownership shall not be transferred until after it has been built upon, then this sale is void, as it contradicts the very essence of a sales contract, which dictates that ownership transfers upon the conclusion of the contract. Furthermore, it contains a potential betrayal of the buyer. Consequently, ownership has not transferred to the buyers, and they are not permitted to sell what they do not own. If ownership had transferred correctly, it would have been permissible to sell an undivided share of it at the agreed-upon price.