It seems to me the DNA results now fit together extremely well, and tell a perfectly coherent story about the descendants of Richard and Isabella. Not proved, of course, and due to the lost records it's impossible to be sure exactly how the lines of descent work; but nevertheless it makes sense. The 3a DNA is shared by (among others) the descendants of Richard (m. Rebecca), the descendants of William (m. Ruth presumably Lambert), the descendants of John (m. Ann Russell), and now, it seems, also by the descendants of Bignal Pace. The simplest explanation of these results is that all of these descend from Richard and Mary, and therefore from Richard and Isabella. In other words, the 3a line is the line of Richard and Isabella. Looks to me like the Pace DNA study has done it again. James Blair