Another person took thumb impression on property papers fraudulently

hello gud morning sir iam from  adilabad dist, we have one property we don’t have any property papers that is my grand father”s sister name is mentioned in mro office ,but she and my grandfather , my father was not alive ,3 years back my viilage real estate agents came to my home that time they told (121 square yards but its 1936 syards)we already purchase ur land but not get registerd so we need ur help to to register,but its not true,then my mother thought to sighn and they did not tel anything about property they taken my mother thumb sign in mro office out side and and given 50000 rs,after 2yrs we get to know the property value is 30.00,000. Recently my grand mother raise a complaint against my mom and that agents in mro office , mro called all of them to mro office ,is theier any problem to my mother plz advice me what should I do my grand mother only legal heir to this property plz tel me what should I do, my grand mother has two kids one i