Owner ship of the grandfather property

My grand father got a 3 piece of land which is in his name. my grandfather passed away some 20 years back and my father too passed away 2 years back. still the property is in my grandfather name. I have one younger sister, mother and iam married living with wife and 2 kids. As my father was working with a small private sector company he had sold 1 piece of land to construct the house. as my father was not entitled for any gratitude's from the employer he did not make any property of his own.my father got retired in the year 1997. my grand father had registered 1 last piece of land on my fathers name. Now i am the only income earning source of the family. i have started my job 15 years back in 2000. Since then i have nurtured my family. i have taken care of my parents with all expenses,i have educated my sister and married to a decent family with all formalities. I have spent more than half of my earnings to take care of my parents, sister. i have not made any property of my own considering my priorities to take care of my parents and expecting the left over property of my grandfather is sufficient for me to survive. Now my sister after getting married, she is expecting the share from grandfather property. Kindly advice.