Grandmother not allowing to sell property gifted to my father by Grandfather

Hi, While serving in the government as a state employee, our grandfather was given a 100 square yard plot of property. He built a house there and gave my father and my aunt (my father's sister) a gift deed for 50 square yards each. In 2012, registration was completed for all parties, and my father's name was changed for his 50 square yard's property tax. My mother and I are prepared to sell the property as a result of my father's passing in 2021. My grandmother won't let me sell the house (as she was interested in giving the entire property to my aunt). My granny has no land of her own. Should I file a lawsuit against my grandmother? Being a Hi, Our Grandfather has received a land of 100 sq yrd land while in government state service. He constructed an house on that area and made a gift deed registration 50 sq yrd each to my father and aunt (father's sister). Registration has been done on each parties in 2012 and property tax is also changed on to my father's name for his 50 sq yrd. Father died in 2021 and since then my mother and I are willing to sell the property. My grandmother is not allowing to sell the property (as she was interested in giving the entire property to my aunt). My granny is not the OWNER of that land as it was given to my grandfather by state govt. Should I file a lawsuit against my grandmother? She is also a state government pensioner.