Ancestral property dispute

Hi, I am vijay from Hyderabad, I have anscestral land at CHEVELLA rangareddy dist .My grand father has 10 acres land in his name in 1954 - 55 year but when it comes to 1974-75 year in that 10 acres 5 acres had been occupied by our neighbour land holders as SHAKMIDAR after some years the SHAKMIDARS changed in to pattadars .Now my grand father died he made the left 5 acres towards five sons he has in 1995 Here my question is what is" SHAKMIDAR" IS My grand father lost 5 acres of land what our neighbour land holder occupied Or else is there any chance to our fathers or I as a grandson to occupy according to law.We are ready to make petition towards that please sujjest me which law is applicable to fight .I am very kind for reply Thanking you Vijjugoud01@gmail.com 9676952290