Adopted sons property issue with adopted father's daughters

Hello All, My grandparents (mother parents) has four daughters and my mother is elder one among 4. since all are daughters, my grandparents did my mother marriage and put them at their house.( i do not know the word exactly in english.. is it adopted or something but in Telugu we say ILLARIKAM ) . After that my grandparents did remaining 3 daughters marriage and they left with their husbands. we 3 brothers to my parents ( elder daughter ) born at my grandparents home and our surname also the grandparents name only but unfortunately when i'm 3 yrs ( elder son & my 2 brothers twins at the age 11 months) our parents both dead so since my parents adopted and henceforth we 3 brothers also. we brought up at grandparents home and in legal all the education certificates also my parents are my Grandparents only. now its been 32 years we are with Grandparents but for some property issue the remaining 3 daughters are suddenly started fighting for property so please advice what is our situation here..? My grandmother died and my grandfather is with me only and completely we brothers taking care of him and he is also not interested to give any property to their remaining daughters.