Cousins of my father trying to take over shop after grandfather death

Respected Sir, the case is abt property partition.. My father is the only son and his parents had died years ago..my grandfather had property which was in two shares...my father was grown up by the sharer means he became my next grandfather..almost whole property he has given to his real sons.. nw my grandfather is no more and his sons means my chacha ji, tau ji nt real are planning to renovate old shops without our permission.. half of that land is in my father's name bt those old shops were run by those tau and chacha...nw as renovtn will start we want our share in that...plz tell wht to do