Rights on Property after widow

I got married six years back in 2010 and separated after four months of our marriage. I am staying with my widow mother. I don't have any kid. My husband is expired on June 24th 2016 this year. My husband purchased three plots in his name and has some Insurance policy and FD. he was working in IT filed as software engineer in private company. after his death i got a call from his office for EPF and pension and other official insurance. and they need legal-heir too. He has two brother and sisters who are married and his parents are also there. and his father has got pension too and my inlaws have lots of property and house in their name. and my in-laws family did not help any to me even for legal heir certificate. So how can i produce a legal-heir and i don't have any kids and is there any right on my husband's plots.the plots documents kept his sister with her. Now what to do and how to apply legal-heir as he was working in private sector. Please guide me and suggest me what to do and how to get the documents regarding plots and i dont know even the survey number too. I just saw the plots... Please guide me what to do and how to do.