FTDNA gives these percentages for a 67 marker match:   1 generation is 43.47% 2 generations is 68.05% 3 generations is 81.94% 4 generations is 89.79% 5 generations is 94.23% 6 generations is 96.74% 7 generations is 98.16% 8 generations is 98.96% 9 generations is 99.41% 10 generations is 99.67% 11 generations is 99.81% 12 generations is 99.89% 13 generations is 99.94% 14 generations is 99.97% 15 generations is 99.98% 16 generations is 99.99% 17 generations is 99.99% 18 generations is 100%   The number I find most interesting is the one for five generations.  My kit is #27450.  I match on 67 markers with kit #22967.  In both kits the donor is four generations removed from the earliest known ancestors, William M. Powell born ca1805 and Allen Powell born 1822.  The above gives us a probability of 94.23% that these men are brothers, or to turn it around, a less than 6% chance that they are cousins rather than brothers.  Cyrus Powell (kit #38739)  is also a 67-marker match.   By way of comparison, another descendant of William M. Powell(kit #37082) has two markers out of 67 that are different from kit #22967(and kit # 22969, another William M. Powell descendant).    Allen born 1789 has a son under 16 on the 1820 census, is known to be the father of Mitchell Powell, who is living in the same household as Cyrus in 1850(and is also recorded in the household of John Powell in 1850).  In 1863 Francis Gibbs, acting as administrator of the estate of John Powell, conveyed to Cyrus Powell a piece of land that was originally in Cherokee County but was by that time in Gordon County, in accordance with a decree dated March 28, 1857.  Cyrus was to hold the land in trust for the use and benefit of "Allen Powell during his lifetime & his idiot son Mitchel Powell".   Add in the Stewart connection, and I'm getting more and more convinced that Allen Powell born 1789 is the father of Allen Powell born 1822.   Chris