I have been amazed at how easily I have been able to find descendants of various family groups over the years. My technique has been to simply find a good ancestry.com file, track the various descendant branches to a geographical location (especially a smaller town), look up living members of that surname in the community, then call or write people in that community of that surname. About 90 per cent of the time it will be a living descendant of a line I am researching. The other 10 per cent tend to be somebody unrelated, but that becomes quite clear in the initial conversation and they will often know of the "correct" family surname members in the community. A word of caution, though. If you want somebody to step up and donate their DNA for your research, be prepared topay for the study. Folks rarely take on the cost themselves. Good hunting!