Crazy DNA question

[patted01]

So I was searching a family surname and came across a person who is famous in US history which I don't really care so much about that part makes for a good story.
What intrigued me is how much I look like him. Doing some research it seems he had no male line but yet my grandmother comes from this surname so it could have been a brother but yet claims of no male line. So to the DNA question I know where he is buried does anyone know if there is a process on getting DNA from someone who is buried?