Will my share be worthless if they sell without me?

That depends upon how the title to the land is. If each of you owns a separate piece of property, you can not stop the sale. If, as is much more likely, your parents said "all of the land we own to our children", then all of you are owners of the entire tract of land and all must approve any disposition, including a sale. The only way your brother can force a sale is to win a suit for partition, which would result in each sibling getting exactly the same dollar amount.? To do so would cost over $15,000 and the current mystery buyer is not likely to wait for the year or so it will take for a court judgment. If your brother will not state in answer to written questions from you [interrogatories] or in public before the judge the details of any proposed sale, the judge is more likely to reject the petition and rule the land is not to be divided. With an hour o two of advice from an attorney, you could probably handle the litigation by yourself, but he would have to hire an attorney. I would doubt that your other siblings would be willing to pay the charges from the attorney merely because your bother refuses to tell you the sales price. There is no reason for your brother to keep the sales price hidden from anyone unless it is below market value or he plans to take a larger share than he is entitled to [he will claim he did all the work to find the buyer, but unless you signed a written agreement for him to be compensated for that, he can not legally charge a commission for the sale. I do not understand why the others have given him a power of attorney. Normally money is thicker than blood. Even with a POA, he is not in as strong a position a he images. A POA allows someone to act for another person who can not or does not want to be present to do something, such as signing a sales document.? He must act as the person giving him the power would want.? That means he must split the proceeds evenly. He can be sued for abusing his position as someone with POA [especially profiting from his actions]. What reason does he give for the secrecy? After the sale occurs, the public records will show what the property is assessed at, which normally would be the sales price. You seem to have a very strong case.