One of my distant genetic cousins is developing an autosomal DNA relationship calculator. This is a work-in-progress at the moment, so he is happy to have folks test and offer suggestions on improvements. You can find more information about his development activities on Robert James Liguori’s Blog. Beta-testing of the basic functionality is now started and he is adding more Relationship Range Providers so that we can calculate with various theoretical assumptions as the basis.
Robert and I have a genetic relationship proven by DNA testing, but have yet to find the paper trail that will point us to our common ancestors. We know that they are on our respective maternal sides as we have an autosomal match between his mother and my maternal aunt. I rather suspect that these distant grandparents are lurking behind brick walls due to illegitimacy on both of our relevant ancestral lines. Best guess so far is that our ancestral paths crossed somewhere in Durham, Yorkshire or Lancashire. Possible names under investigation so far: Whitehead, Horsfield, Bailey, Shepherd, Mitchell, Manners, Webb.