Anyone at all curious about your ethnic heritage should spend a few minutes at FamilySearch.org
. I think you can only put in dead people (relatives, or famous, you name it), but if you get a hit, it's amazing how quickly it can fill out your family tree.
The site is run by the Mormons, who are religiously obligated to do genealogy, but they've put so many resources into this, they're effectively the clearinghouse for everyone, regardless of faith or ethnicity. I was raised Mormon, so my heritage is particularly well researched: following a pure paternal line, I can go back to about 1520.
If you can't find one of your own ancestors, but still want to see how it works, look for Samuel Mitton, died in 1992. Then click on the ancestral file entry. On the right, you'll see one link for "family" and another "pedigree".