My sister being harassed by her In-laws after her husband's death

Sir, My Brother-in-law (aged 37 yrs) died two weeks ago due to some medical complication.He has left behind my Sister and her two children (8 and 6 years old). Now, as they don't have any financial means to cater to their daily expenses, my sister tried to ask for money from her father-in-law, but he summarily rejected it by saying that go and ask your mother. Then we told her father-in-law, that we would be taking care of her financial needs relating to her children's education and he should take care of her daily needs like grocery and all. But he is not ready to even this. Then, we put forward another option that if he could take care of the children at home than she will work somewhere to earn money, but he is not even ready to this. The house my sister lives in is in the name of my deceased brother-in-law and his mother who is also dead. What all legal options do I have to make sure that my nephews get their due part from that house and what is the procedure for the same. Thank you