Who Is The Legal Heir

Hello Dear Lawyers My sister who got married in 2015 to a man under Christian marriage law in Gujarat, who was divorced in 2012 and his ex wife got everything he ever owned. When he married my sister he told her that he is basically broke man except his government job. During their marriage he was abusive after drinking he would get violent so that my sister came to live with my mother. After 6 months or so my sister waited that he would come to pick her up but he did not make any efforts to contact her. My sister kept calling him and there was no answer so finally she went to his parents house to her surprise they told her that he passed away and she was asked to get out of their house. My sister's in laws did not inform her of her husband's death and last year we found out that her mother in law and the ex wife had put claims to his pension and insurance money. The reason they did not inform my sister is to illegally take possession of everything her husband had and kept his death secret. But thanks to our God Almighty he revealed their evil plan. Now what can we do. Does the ex wife claim anything after divorce. He had 2 children with ex wife do they claim anything. Please help. Thanks Sonal