Dewey was actually John Ephraim Dewey Deaver, born 9 March 1900 in Young Cane, Union Co., GA, and died 16 Feb. 1920 in Blairsville, Union Co., GA. So you are right, he died before Mae Belle and apparently she remarried. So they must have married in 1919, or in very early 1920. The Union Co. courthouse should have their marriage record.
His father was John Stanhope Deaver (b: 1878 in Nottla, Cherokee Co., NC) (d: ? Buried: ?)
His mother was Tennessee Frances "Tennie" Young (b: 18 July 1875 in Young Cane, Union Co., GA) (d: 1963?Buried: ?)
I did not know about the brother named Jessie! (Jesse?) I only have these siblings for Dewey:
Henry Newton Deaver, b: 9 Feb. 1903, d: 19 July 1946, buried: Ivy Log Cem., Union Co., GA
Wayne Deaver, b: 24 July 1911, d: 1963, buried: Liberty Cem., Union Co., GA. (Not to be confused with Old Liberty or New Liberty cemeteries).
Margaret W. Deaver, (twin to Wayne); I do not know if she lived to adulthood, or who, if anyone, she married.