"We're all cousins" is something my grandmother said to me regarding her family and my grandfather's family. Both families were long-time New Englanders who could trace their ancestry back to colonial times, so this was literally true, though she didn't know what the exact connection was. I think they were probably fifth or sixth cousins, so not exactly what we today would call "kissing cousins".
Still, I've found over the years in my genealogy research that the general sentiment that we're all related is true. So for years I've been researching to see if my family and my wife's family were also related. And I think I've finally found the connection. It's way, way back, of course. As far back as a fellow by the name of Alberic the Second, who was Duke of Dammartin in the late 12th century. http://en.wikipedia.org/wiki/Alberic_II_of_Dammartin According to the genealogies I've found online, he is one of the ancestors of one Henry Adams, one of the first colonists to the early United States. Henry, in addition to being the Great Great Grandfather of President John Adams, was also the Great Grandfather of one Hannah Adams, who is one of my wife Raquel's ancestors through the Pond family.
But back to Alberic. He was certainly a very important person, as his Granddaughter Joan de Dammartin was the Queen of Castile. Their progeny included Eleanor of Castile, better known as the Queen of England alongside her legendary husband Edward I of England (you might know of him as "Longshanks" who Mel Gibson fought against in the movie "Braveheart"). Online I have found several documented connections of my family to King Edward and the Plantagenet family. This is my connection, as I know I'm descended from Edward, and his son and grandson, Edward II and Edward III.
Alberic's progeny also included one John of Gournai (there are various spellings of Gournai). John's daughter Elizabeth married a country lord named John ap Adam http://en.wikipedia.org/wiki/John_Ap-Adam,_1st_Baron_Ap-Adam in the early 1300's. These folks seem to be the wellspring of the entire Adams clan. Interestingly, there is another connection which I found that suggests that John of Gournai was William the Conqueror's great great grandson, but apparently that is historically in dispute. Interesting how much trouble people will go through to document or disprove royal lineages. I definitely am descended from William, as his lineage also passes through Edward and the Plantagenets. Anyway, I'll keep digging because I'm sure this won't be the last crossover I find between my wife's family tree and mine. I'm sure I'll find a royal connection for her as well, perhaps along one of these same lines.