What should a brother do concerning his father's grave, which was built with bricks in 1970, knowing that building upon graves and desecrating them are both forbidden?

It is disliked to place bricks in the grave, and if they are placed, it is not permissible to exhume the grave to remove them, because exhuming graves is forbidden without a legitimate Shari reason. However, if the bricks are on top of the grave, they must be leveled with the ground, due to the hadith: "Nor any elevated grave but you level it."