Mike,
Yes they are related, Col. Isaac Folsom was father of Col. Sampson Folsom and brother of Isreal Folsom--that makes him his Uncle, he(Isaac)must of got title Col. in a earlier war?

Sampson had served in the Chickasaw Senate and a signer of the 1855-56 land deal with the Choctaw. He was Chickasaw from his mother, Underwood.It's interesting that he is also doing Choctaw affairs/both tribes.
Sampson was 'well to do' pre-war married into the wealthy Colbert line-plantation's/business's Etc.
A flavor for a uncle to exchange money looks likely to me.