What do these 11 Presidents have in common?

Georges Washington,John Quincy Adams, John Tyler, James Garfield, Theodore Roosevelt, William Howard Taft, Herbert Hoover, Franklin Delano Roosevelt, Harry S. Truman, George H. W. Bush, and George W. Bush.

Could they all have had their biographies published ?

Several of them, at least, were descended from one of the Edwards of England.

I think that makes them descendants of Charlemagne.

They all were descendants of French Huguenots according to this very interesting Source
If you don't want to read it all, find the "Huguenot Contributions to the American Colonies" part.