Share for grandson property.

Hello respected Sir, I would like to brief my situation. Property is in chennai my father's family stay there. I live in Bangalore with my mother's family. Parents got married in 1986 I was born in 1988 later father died in 1991 thereafter no contact with father's family till now. Now my age is 26 only son. I heard there is a property belong to my grandfather he is no more even grandmother is dead. My grandfather has 3 son's(including my father (late)) two daughter. Each one have 1son 1 daughter. Now I would like to know what is the 1st step I should do to receive my property legally. And also I don't know how much property my grandfather had. My mom says there is more than two property in your grandfather name. How to get those details? Kindly guide me. What if my brothers got married and had sons now will it be shared to them and what if they have sold the property or if the property have transferred to my father's brothers without our knowledge. But we are sure it's not transferred. Thanks in advance.. Waiting for your assistance