Claim by stepbrother regarding assets

My father : Late T. Venkateswarlu(constable) had two wives 1st wife died and my father married the second wife. First wife has two sons and my father legally given the 2nd child of first to adoption to relatives. 1st child is elder and he is major now Second wife has one son and it’s me Issue: my father is police constable and died in service, at that time 1st wife 1st son is minor and he is under his mother side people guidance and guardian, and we have came to agreement that my father house and all his died service money will be for 1st wife son and job and pension for my mother who is second wife We made a agreement on this and proceeded Now first wife first son is calling us and asking to give the share in our earned assets and also asking us to give money and threatening us that the govt job my mother is working is his father’s job and saying he has the right to ask the share in our money and also asking us to give salary amount of my mothers job Note: 1st wife 1st son received the pension upto 18 years