Property Issue

My grandfather had 2 wives (my grandmothers) both were siblings. They did not had any child for years. So, they both adopt a infant baby son from their younger brother (My Father). After sometime, my grandfather bought a 500 sqyd land (our present home) and again 500 sqyd land (Uncle’s present home) just beside to it and on his name. After two year later my small grandmother got pregnant and delivered a child (My Uncle). My grandfather raised both of them equally. My father had some issues related to his mental health in his teenage after some time he got married to my mom. Two years after his marriage he got several serious issues with his mental health, due to which he were admitted thrice in state owned Mental Hospital. I uncle got greedy and want take over all property. So, my grandfather made a Will deed with the help of his lawyer. He declared that - “All of my property and belongings are only belongs to both of my sons and no one can claim on this” And he did not disclose which part of land belongs to which son. My grandfather died (20 years ago from now) and our relatives distribute all land and jewelleries equally in presence of both of my grandmothers and my father & my uncle. Our present home’s “House tax –Water tax –Electricity bill” transferred on my father’s name and uncle’s present house documents “House tax –Water tax –Electricity bill” transferred on uncle’s name. (20 years ago) After some time my greedy uncle fooled my father and asked (10 years ago from now) for our original land registry which were on my grandfather name and my father gave to him and none of us know about this. After some time when my father asked for registry he refuse to gave him and threaten him. When our relatives intervened and tried to take registry, he refused and said that my father didn’t gave any registry or documents to him. After 3 years later my father died. All documents “House tax –Water tax –Electricity bill” transferred on my mother name. Last month, 2 men came and said that “this house is on sell and we want to buy it” and some other person came to us last week and said “this house is on sell and he want to buy it”. We refused that this is not for sale. Please, advice me what should i have to do to protect my land.