Do a Y-dna test to find out what Blackwell family you are from.
Family Tree DNA has a Blackwell project, many seperate families lines can be seen through the results. The Virginia Blackwells have results so it you test you will find out if you are related to them.
Robert Blackwell is the admin of the project and has a ton of knowledge on the VA family.
There is a sale till Dec 31 for the test