Im related to George Washington!

George Washington had no known children, only step-children from Martha's previous husband Daniel Custis. So no grandchildren, great grandchildren, etc. This has been the accepted lineage for over 200 years. Lots of nephews and cousins, though. DNA could show this to be untrue, however.
One of Martha's grandchildren was George Washington Parke Custis, of the Arlington estate, now National Cemetery. His daughter Mary was Robert E. Lee's wife, who inherited the estate. The property was seized by the Federal Government and made into a cemetery. One of the early burials was the son of the QM General who was killed in the war.