Legal heir certificate

My husband passed away recently, he took LIC policy before our marriage, at that time he nominated his monther in LIC policy, his mother also passed away 1 year back, but he did not change nominee details in LIC policy I have been told by LIC agent that I would need legal heir certificate, my mother in law's death certificate and original lic bond papers of LIC policy I don't have my mother in law's death certificate, LIC bond papers, those are with my husbands brother and he is not cooperative he is trying claim policy, In this case what is the process to claim LIC policy and how to get legal heir certificate what will be the estimated cost involved in this all legal process If I get legal heir certificate will i be responsible for my husband's ongoing house loan, I don't want to take responsibility of the housing loan because am not going to stay in that house and in future also am not going to claim any kind of rights on the house My husband is having other properties also(agricultural land) I am not expecting any of these but I am only expecting LIC policy claim. Note: I don't have registered Marriage certificate, I have only photos as proof of Marriage. please suggest what should be my next step