Ron
First let me apologize for not returning your phone call, I'll explain later.
The two brothers of Edward M. Riley you seek are Andrew Jackson (Jack) Riley and George Washington Riley, both enlisted in Tyler County, Texas in the 25th. Texas Cavalry.
Doyle Taylor's post indicates the 25th. Texas Cavalry(Dismounted) was among the units surrendered at Arkansas Post as does the CMSR's of these two men.
Send me a email and we can discuss the service records and family records a bit further.
Happy Easter,
Mitch