Obtain death certificate

Dear Sir/ Madam, One of my friend is in need legal support. His grandfather died before 20 years. After his death the four legal heirs arranged for amicable settlement on dividing the properties into four shares. My friend father was given the share of property which includes a common land which will be used for government purpose. Actually before 40 years government authorities noted those property under BOOM THANAM scheme. But the property is managed by my friend family and not availed any record from the local administration authorities due to lack of awareness. Now my father had discussed with his brothers and they all are ready to sign the no objection documents legally which will make the properties to my friend father. While processing for this in the local registration office they informed to get the heirs certificate as well as the grandfather death certificate Which they have not obtobtained till now. Request you to provide the legal guidelines to obtain the grandfather death certificate, legal heirs certificate, and to get the property land without any encumbrances in future. Thanks.