Quitclaim Deed

My great grandfather purchased a tract of land in Texas in 1938. Upon the deaths of my great grandfather and great grandmother, the land was deeded to their children: my grandfather, and two great aunts. My grandfather died in 1976, and left his part of the land to my grandmother. One of my great aunts died in the 1990's and left her part of the land to her husband and the other aunt died in 2000 and had no children or spouse to leave her part to. Someone came along in 2004 and acquired a quitclaim deed on all of the land and sold it. All this time we are were still paying the property taxes on the land. My grandmother died in 2006 and left the land to her estate (which my mother has control over). We have the deed to the land. The man says he sent letters to the owners (who all happen to be deceased and no longer at the adresses he sent the paperwork to) and no one showed in court. Do we have any rights to the land now? or does the new owner get it all?