Success! I have done some online research and believe that I have found that Gen. James McIntosh was fourth cousin to Col. D.N. McIntosh. I also discovered that James' brother John Bailie served the Union from Penn. Here are my resources:

http://freepages.military.rootsweb.com/~virgilgw/third/mcintosh.html

http://www.rootsweb.com/~gamcinto/mackintosh-genealogy.html

http://www.virtualology.com/lachlanmcintosh/

http://digital.library.okstate.edu/chronicles/v010/v010p310.html