Hugh and Robert Cowan settled on Octoraro Creek, Chester County, PA about 1720. The relationship between Hugh and Robert is not known, but it seems likely that they were related, perhaps as shown in the accompanying diagrams. Each had a number of sons who migrated west to Cumberland and Westmoreland Counties, and raise families. One of these sons, Person:Mathias Cowan (1), son of Hugh, would settle in Westmoreland County. A YDNA test for one of his descendants shows that this line is characterized by the I1 Haplogroup. As of may 2011, about 5% of the kits in Cowan YDNA Project correspond to the I1 Haplogroup. In Contrast, about 90% of the Kits in the Cowan YDNA project correspond to the R1 Haplogroup.
A number of other lines of Cowans settled at an early date in Old Chester County. Of particular interest here is the Cowan's Gap Cowans line which settled in Cowan's Gap of Bedford/Fulton Counties in Pennsylvania just before the end of the Revolution. Among these early Cowan's Gap Settlers were Person:Samuel Cowan (17) and Person:Hugh Cowan (7), Samuel settled in Cowan's Gap, and Hugh settled a few miles to the west along Licking Creek, and were on the tax rolls as early as 1781, indicating that they had been present in the area prior to 1781. Given the fact that they settled near each other, and secured land warrants for their property on exactly the same date in 1783, Hugh and Samuel are presumed to be close kin, and perhaps brothers.
Several individuals traceing their descent to one or another of the Cowan's Gap Cowans have taken the YDNA test through FTDNA. Their results give a characteristic YDNA signature. A single individual traceing descent to one of the Octoraro Creek Cowans has also taken the FTDNA YDNA test. Their signature is very similar to that of the Cowan's Gap Cowans. This suggests that the two groups (Cowan's Gap Cowans, and Octoraro Creek Cowans share a relatively recent common ancestor. Taking these results at face value it seems likely that the Cowans who settled in and near Cowans Gap about 1780 are descended from one of the Octoraro Creek Cowans, though direct genealogical evidence for this is currently lacking.
The above conclusion is likely to meet with considerable skepticism among Cowan researchers. Among Cowan's Gap researchers the idea that they descend from a line that was clearly in place in Pennsylvania by 1730, flies in the face of the commonly accepted story of their family. This story (commonly referred to as The Romance of Cowan's Gap) holds that the family descends from a John Cowan who settled at Cowan's Gap shortly after the end of the Revolution. According to the story John was a British soldier during the Revolution, and his wife the daughter of a Boston Merchant. Her father disapproved of the marriage, and so the couple eloped after the end of the Revolution, moving to Cowan's Gap in PA.