Misuse of Ancestors Donated land for Matt-want to take back to fulfill

Sir, I am a Hindu. My late grand father's lonely cousin having no children donated 2 acres of land to a trust (about 50 years back) to construct and manage a matt. Subsequently over the years the trustees have started selling the land illegally and many commercial and multi storied residential buildings have come up in the site. There is no trace of any matt and religious activities are seen. We 3 cousins (sons of 3 brothers born to my grand father) understand it is possible to claim back the donated land. Hence we want to take back the land and manage the trust now to fulfill the wish of our ancestors. What is the legal procedure? Pl clarify. thanks