YDNA passes from father to son exclusively, so yes, the DNA would have to come from a direct line male descendant of the referenced James Kerr, or a be a direct male descendant from Jmaes' paternal line ancestors, to be useful in identifying a likely lineage connection. James Kerr and Mary Sproule were born about the time of my grandfather Robert, son of John James Carr (Kerr), so the connection would need to be with an earlier generation of the Kerr paternal line. My great grandfather would have been 34 when the James Kerr being discussed here was born, so it is possible that the connection is even two generations prior James. If anyone knows the pedigree of James back a few generations, and possibly the expanded male line, I would be grateful for that information.
There are many DNA tests available at relatively low cost these days that can identify potential relationships at the cousin level as well as maternal and paternal line ancestry, and even ancient genetic line affiliation. Personally I find these DNA haplotypes are as important a genealogical tool as any other that I have at my disposal. The cousin and maternal line tests have been very useful. I am still waiting for a connection on the paternal line DNA, which has a few characteristics that are on the uncommon side, which makes finding connections rare, but more likely to share the same paternal line when found.
If anyone knows of a living male whose direct paternal lineage extends from the James Kerr being discussed here, or from the paternal line of his father, grandfather, etc., I would very much appreciate being put in touch with them so I can ask them to take a YSTR DNA test, at my expense if proof of a potential link to a shared paternal line exists. This test identifies nothing beyond potential relatedness, so there are no worries about revealing anything personal about the DNA donor. I encourage all of you to take at least a cousin test, you have a good chance of linking to someone who can expand your family history knowledge in some way. Plus, we can see if we do likely share some recent ancestors.