Disputed property

In year 2006, the father of our  client ,who is the younger daughter, died suddenly due to heart attack without leaving a will of property at the age of 52 years. He had a wife, two daughters and a son all children studying. Since the wife was illiterate the cash, gold and silver  and property was handled by eldest sister . Mother died slowly due to lack of medical care in year 2013. In year 2015, post to her marriage, the eldest sister, now does not want to share any amount of property. Following points are to be noted:-

1. one bank account of father is yet unclaimed
2. All accounts of mother have been made joint account of eldest sister and funds transferred to own accounts
3. She is giving no accounts of gold or silver, maybe kept in a joint locker of mother and hers
4. She has spent a lot of money from these accounts for her personal luxury requirements
5. She has bought land from these money
6. She had emptied the funds from the accounts of small sister on behalf of small sister’s marriage
7.  She is not giving all fixed deposit details done by her father on small sisters name
8. Not giving details of own house/property papers
9. Not giving details of cash at home at the time of fathers death

What is the best way to approach and best possible relief sought?