What was the cause of the death of your father. Did he expire while he was on job.
You may speak to the Manager HR, and study the policy of the company.
You can also discuss with the Secretary/President of the Union of Employees, and obtain clairty on the rules and policies.
You can also discuss with senior emplyees in the same department in which your father served the company, and obtain clarity on the rules.
You can also speak to the NGO/Welfare associations working with the company or active in your area.
Accordingly, you can take up the matter with the Management, in writing.
You may seek legal help from local service lawyer.The lawyer would know the rules, and can help you persue the case.