I2a2b Isles B1 Nance

If you look on page 2 of the FTDNA Y-Haplogroup I2a Project - Y-DNA Colorized Chart, you will notice that Nance is the dominant Surname in I2a2b Isles B1 group, with 7 of 28 (25%) of the members in that group. Notice that Grimes, Grant, Wrensch, Williams, Blake, Sharpe are all in between the Nance results. All of the I2a2b Nances in this group are related and have the same common ancestor from Cornwall, England. They are all my cousins. Does this mean that all the names in between actually had Nance fathers? We have traced down two of them and found that our ancestors were in the same counties at the same time. Does this mean that it is highly probable that all of the aforementioned names actually had Nance fathers? How else could the 67 marker test match exactly between for example Nance 140580 and Grimes 31207? Those are FTDNA kit numbers.
I cannot post the link or I would have. Thanks in advance for help/constructive criticism....Chris Nance

The ordering in the FTDNA tables isn't based on similarity, it's based on STR values from left to right, so individuals being in-between others doesn't mean much by itself. In particular, Grant, Wrensch, Williams, Blake, and Sharp all look unique enough to not strongly suspect that they were once Nances.

The most curious one is indeed the Grimes sample. He's also an outlier among Grimeses, and Grimes, unlike Nance, is not a Cornish name. So it's a workable hypothesis that Mr. Grimes' ancestors were actually Nances... but not proven unless we have proof that his Grimes line was in the same place at the same time as the Nances, and other Grimeses along his paper trail are testing as different haplogroups (proving a NPE). I don't know if proofs of those exist.