OK, my cousin Martha has outdone herself in tracing the history of my dad's maternal side, the Hendersons. I am sitting here in awe of her research skills.
Below, my father's mother, Cordelia Henderson Thompson. She is the daughter of James Lewis Henderson and Martha Beall. The Hendersons were originally from Virginia.

I am related to George Washington, Thomas Jefferson, Robert E. Lee, and Queen Elizabeth II. For someone like me who is a history buff, that's mind-blowing.
Below, Martha's email to me explaining it. [Martha's words are in blue. Links to other sites are underlined] The plus sign means married.
above, Augustine Warner II
Augustine Warner II + Mildred Reade [Mildred was the daughter of George Reade** & Elizabeth Martiau, daughter of Nicholas Martiau .. known as the first American Ancestor of George Washington, for whom the President was named. Nicholas, a Huguenot, went to England, naturalized, became an engineer, came to VA 1620 as representative of the Earl of Huntingdon and established Yorktown.]
Augustine II's sister Sarah married a cousin, Lawrence Townley and their daughter Alice m. Grymes .. down to R Lee. [This page explains it more thoroughly.]
**George Reade traces back to Edward III through his son John of Gaunt, his daughter Joan Beaufort + Ralph de Neville, Earl of Westmorland, plus the Percy Family, Earls then Dukes of Northumberland.
Augustine Warner II [sometimes known as Jr.] had these children:
This is the good stuff, and hits all highlights of history Elizabeth Warner + John Lewis .. Her sister Mary was the grandmother of George Washington, her sister Mildred is the 7th great grandmother of Elizabeth II, Queen of England, thus our 1st cousin 8x removed, or 9th cousin
[Elizabeth Warner and John Lewis had a son, Charles]
Charles Lewis + Mary Howell
[he had a son, Charles, Jr.]
Charles Lewis Jr + Mary Randolph [her sister Jane married Peter Jefferson, and they were parents of Thomas Jefferson]
Charles and Mary had a daughter, Elizabeth Lewis
Elizabeth Lewis + Bennett Henderson .. Eliz is 1st cousin to Thomas Jefferson, and 1st cousin, 2x removed of Geo Washington. She is also related to Meriwether Lewis [of the explorers Lewis & Clark]
[One of the children of Elizabeth Lewis and Bennett Henderson was Hillsborough Henderson]
Hillsborough Henderson + Mary Price
-- they had a son, Francis Marion Henderson.
One of their sons was James Lewis Henderson
James Lewis Henderson married Martha Beall
and so on ... to us [their child Cordelia is my grandmother]
There was much intermarriage between the Randolphs, Lewises and Jeffersons.
Fun, huh? Ancestry got very interesting once I stopped with the confusing
Henderson background and went to Bennett's wife, Elizabeth Lewis, and hit
the jackpot. You can join the DAR (many times over), the Colonial Dames,
the First Families of VA, etc., and Nicolas Martiau (pronounced Mar-Show) is
the first direct line Gateway ancestor. The first relative on the 1st cuz side
was a man called George Percy, came on the first 3 ships to Jamestown in
1607. He is a son of the 8th Earl of Northumberland, Henry Percy, and his
wife Catherine Neville, from the above mentioned de Neville/Beaufort line.
The Earl resided in Alnwick Castle, where the Harry Potter movies were
shot!
The Inn at Warner Hall is the restored home of Augustine Warner, our ancestor. I'm thinking that's where we need to have a reunion sometime soon...