Sir Nate,
I don't know when true blood ends, but since we all have more than 5 MILLION 20th great grandparents, I'd wager the Marshall and myself share very few chromosomes!
The fun of finding these folks in our family tree is only that, fun. It is meaningless otherwise.
Sir Humphrey
What if one of the families still bare the name Marshal?
Unrelated in a way. Marshal had no male grandchildren (edit for clarity - *born of his male children*), and his female children would have taken their husband's name. If there is another Marshal in the chain, it's another Marshal family that married into William Marshal's descendants somewhere along the tree.