How will the property be divided if my grandfather had 3 brothers

My grandpas were 4 bro. The younger and middle bro got 5 ekar, 3 ekar land because its no so far from home and another 2 bro got a combine of 16 ekar land as 8-8 ekar. The younger and middle bro sold their agricultural land. My father brought 3 ecare land from middle grandpa. We have the registry of that. But unlikely the patwari not dismissed the middle grandpas name. Now all of my grandps are no more. But the middle grandpas step son send us a notice for his share. Hope you understand the case. Please suggest us how can we defend our point.