Acquiring Father's Brother's Property who is expired

Hi, I am from Karnataka. My question is we have ancestral property which was acquired by my grand father's grand father. My grand father had two brother's one of them sold his share to third party. The second brother of grand father's property is in his son's name and son (For easy I will call father's step brother) expired around 30 years back. This son didn't had kids and his wife is still living in some other place. My direct grand father had two son's my father and my father's brother. My father's brother also not having kids. Now my father's brother and father are asking to develop the property which is belonging to my father's step brother. I am bit reluctant as I don't know who will be the hair's of this property. This property was in my father's brother hand from more than 30 years. My grand father is expired in 1970s. My father has around 5 sisters and one of them is already expired. So my question is who all have the rights in my father's step brother's property? Can we prove the share by mentioning the Adverse Possession of the property?