How about this case. Lewis DeRussy was born in NYC, graduated from West Point in 1814, and served 29 years active duty in US Army. Was assigned to Ft. Jesup, LA, in 1826, so was in Louisiana for 35 years when the war broke out (considerably longer than your scenario). Raised his kids in LA. Didn't have a plantation and slaves, but his second wife did. When the war did break out, he took his own regiment north to fight the Yankees. But when he found his brother across the way from him, he resigned his colonelcy and went back South. Continued to serve his new country. His brother, meanwhile, went west and continued to serve his old country, but out in California. (Their kids, meanwhile, fought each other at Malvern Hill, one as a Union general and the other as an officer in the Washington Artillery.) His niece, who was raised by Lewis, was born and lived most of her childhood in New Jersey, but was married to a CS officer and had strong Southern leanings. Legend has it that the DeRussy home near Natchitoches was not burnt because Banks was a friend of the Northern branch of the DeRussys.