Testament

Dear Sir/Madam, Im from Bangalore. my grandmother (My mother's mother) and own a property which is still registered in her father's name (my great grandfather). my grandmother had many brothers and sisters. but all her bro's agreed to let to use that property between with my Grandmother, my grandmother's sister and her bro (3 members). My grandmother's younger sister and younger bro ( both passed away) have children. now only my grandmother's sister's sons and daughters & grandmother's brother's sons and daughters are using the property. My grandmother is alive still (94 years old). Those children of my grandmother's sister's and bro's are not giving share to my grandmother. As she may pass away any time. we have not registered any case against them. So please help me whether shld we take and will or testament or any power of attorney from my grandmother to fight for that property in order to gain our rights even after grandma passes away. please help. My email id is stanley@kristujayanti.com