ancestral property

Respectable Sir, we need your precious legal advice regarding our ancestral property, do we reserve due right over our ancestral property if outsider without our consent constructed a building over that particular piece of land for commercial use for a couple of years from now. recently we come to know that the said property solely named after our great-grandfather and he never sold to any person or agencies . after that we approached to the person who constructed the building and using it for personal gain. he refused to provide any authentic document till now, and later on, he showed sale deed (nothing else) of third person who earlier from him occupied the land for some time then secretly sold it to above mentioned person by only handing over him said sale deed . one thing need to be noted here that the sale deed is not approved and has no relevant stamps or even witnesses id copies or names are mentioned in the deed. so does this this deed considered authentic and as I mentioned earlier that the property still remains in our great grand fathers name. we asked the tehsildar of the area he head no ears to our mater and said, ” you have no right to claim ” becuase it is in your great grand fathers name he had not distributed to his family during his lifetime and aslo its become too late for you know to claim it. so any one who has possession our your great grand fathers property it belongs to them right now you cannot or have any right to do so.” these were the remarks of Tehsildar.

kindly briefly guide us regarding this matter because we do not no the know how’s of the issue. we will be thankful to you for regard.