TIL: George Washington's Step-Great-Granddaughter was Robert E. Lee's Wife

https://en.wikipedia.org/wiki/Mary_Anna_Custis_Lee

Also, the last heir to Mount Vernon before it was sold to the Mount Vernon Ladies Association was John Augustine Washington III, who died in the early years of the Civil War as a Confederate Solder.

https://en.wikipedia.org/wiki/Mount_Vernon#Preservation,_legacy_and_tourism