You need to review all documentation with respect to the signing over the land by your mother to your sieter and brother and law. If the transfer was a straight gift as opposed to a sale, there really is not much that the estate of your mother can do about the situation that you have written about.  I suggest that you consult with a real estate attorney further about the facts that you have written about and to review all documentation concerning the transfer of title to the land that you have written about.