To Play The Role As Karta In Family

My father passed away last December, I am the elder son and three sisters and younger brother, who is an Advocate, all are married, my mother and brother are hiding from me all economic facts that my father left after death about the movable property, agricultural income, savings, insurance, etc. I do not expect partition but want to know all economic affairs to control unnecessary expenses as I am also a low-income earner I need to procure savings for all family members but both are hiding everything from me. But as an elder son, I am right to play the role of karta for the family. What is the way to solve my problem?