First of all, verify the Pahani and Patta Passbook under whose name it is issued; you can get it by consulting the concenred revenue authorities, and if necessary, you can apply under the Right to Information Act as well to see the holders of the owner of the concerned property records. If the land falls under the agricultural land and there is any other relevant records indicating the existing owners of the property, you an also obtain the same. You can also go to the local sub-registrar or district registrar office to obtain the "Encumberance Certificate" wherein you can also findout the names of the existing and past owners of the property and any encumberance thereof. In general, your mom may be entitled to 1.25 acres if the whole 5 acres is shared equally among the four sisters. In this regard, you have to see any will specifically signed by your grandmother or something. If the property your mother's sister is holding is for more than 12 years or prolonged period, you have to check with the adverse possession rights accrued to your mother's sister as well that totally makes you disqualified to obtain any lawful remedies in an effective way. Depending on the property value, it is always better to take guidance from an effective and efficient lawyer. Hope you will have some basic idea to do further research to know your case status based on the above guidelines. Without spending minimum reasonable money for the above transactions, if you try to extract everything, it becomes very difficult for you since it will kill most of your time and energy and makes you weak and frustrated, so, spend minimum reasonable money if you are poor, to effectively achieve your property back if you have any case. Good luck.