Looking for Charles Virden of Oklahoma

My GGF, Joseph P. Virden (b.3/1870)apparently had a brother, "Charles". However, I do not see him listed as child of Joseph's parents, Eli Thomas Virden (b.11/3/1841 d. 9/25/1927) and Susan, or Julia (Joseph's second wife). But, I have a picture post card from Joseph P Virden which is addressed to "My dear Brother, Charlie Virden" of Warlow, Oklahoma.