Brother in law wrongly claiming insurance amount after death of sister

My elder sister passed away in an accident recently.she married a guy 6mnths back without my parents permission..my parents didn't approve this marriage because he was bad guy,he is used to all bad habits. he is not educated,not earning and he is even into bettings and lost money .he used to emotionally blackmail her and take money from her.. during this 6mnths when my relatives and mom spoke to her on phone she said she is living good.but recently we got to know from my sister's friend who is also injured in this accident that she is not happy during these 6months .he just used her financially and he made her to sign surity for all the debts he made.now he is proceeding for insurance and we don't want him to receive that money. Let me know waht to do? Please kindly tell me what are the acts applicable for this situation in order to stop him from getting insurance money and to take legal action against him for using my sister financially