George Washington Parke Custis, 1781-1857. He was the step-grandson (and adopted son) of United States President George Washington, was a nineteenth-century American writer, orator, and agricultural reformer. He was the grandson of Martha Washington through her first marriage to Daniel Parke Custis. he inherited vast sums of money, land and slaves. During the War of 1812, Custis volunteered in the defense of Washington, D.C., at the Battle of Bladensburg. Cousin, Arledge line.