Some of the members of group 21 FTDNA may know about the collateral lines. One caution: two old VA families lived side by side, both having John Martins. Find out which group you match by FTDNA. My line is featured in Stella Picket Hardy's Colonial Families of the Southern US, and includes descendants of Abram to John 1685 and Zachariah 1690. A friend of mine on ancestry is connected with the Abraham Martin you mention, and appears to be descended from John's son Thomas. Check your DNA. We stayed in the area around Franklin County, GA across from Anderson/Abbeville, SC for the past two hundred years, and did not keep track of people who moved away.