Job in bmc after father's retirement

My father worked in BMC hospital in mumbai.he had worked as sweeper for some years afterthat moved as post mortem attendant in mortuary department. Now after the retirement, my brother is legal heir to get bmc job as P. T. Case, but department is not recruiting him saying that they don't offer job to any employee promoted to post mortem attendant. If my father were sweeper, they could have offered the job. My question is, can post mortem attendant son get job after father's retirement ? Or if only sweepers son can get? Now, Problem occurs here, when my father was shifted in mortuary department, it was not done on paper. They dont have any promotion letter, he was transferred because they did not have enough staff there. So they called my father and instruct him to work there. My father had just obeyed it with out knowing any consequences. Since he was not much educated, he dindnt know to get promotion letter or any thing, even they didn't offered. He was working in that department with salary of sweeper grade. He was hoping that after his retirement , his son will get job just as other worker's were getting. Now it has been five year after his retirement, he was following up with these government body everyday eversince he retired. He was travelling from home to their office everytime to get this work done. But These people are not forwarding his file and not even seeing it. With all that problems on head one day he passed away with heart failure. Its been just one year ago. Now my brother is also doing the same thing but no luck yet. Request you to please advise if something wrong is being done by them, so we go against them or we are Wrong in any case.