It is more than likely that Sanders was born in the Covington Township area, although the obituary of Addison Monroe states he was born in Okawville. Obituary of Addison Monroe Summers lists this fact. Nashville News).
!Leonard G. Tucker was appointed Guardian of Sanders, Addison, and Zachariah on 18 Sept 1850 by the County Court of Washington County, Illinois. (I can find no evidence of this act in the probate records, but supporting documents state that this is so.)

Sanders served with the 44th Illinois Infantry Company F until he re-enlisted in the 16th Illinois Calvary Company I, his rank was private. He was captured on 3 January 1864 and was sent by transport train to Andersonville Prison in Georgia. He was released 1 December 1864 and exchanged for Southern prisoners in Columbus, Ohio.

Illinois State Archives
http://www.cyberdriveillinois.com/departments/archives/databases.html
state this information:

SUMMERS, SANDERS
Rank PVT Company I Unit 49 IL US INF

Personal Characteristics
Residence ASHLEY, WASHINGTON CO, IL
Age 18 Height 5' 5 Hair LIGHT Eyes BLUE Complexion FAIR Marital Status SINGLE Occupation FARMER
Nativity IL

Service Record :
Joined When FEB 1, 1862
Remarks DROPPED FROM ROLLS AS DESERTER JUL 1, 1862


Andersonville Prison Georgia gives this information:
http://www.civilwarprisoners.com/search.php?database=andersonville


Record_id: 35377
Name: Somers, SANDER A.
Alternate spelling of last name: SUMMERS
Year born: 1844
Rank: PRIVATE
Company: I
Arm: Cavalry
Regiment number: 16th Illinois Cavalry
Date captured: 1/3/1864
Location captured: Jonesville, Virginia
Fate:
Exchanged December 1, 1864; mustered out August 19, 1865 at Nashville, Tennessee.
Remarks:
RELEASED 12/01/1864, EXCHANGED COLUMBUS, OHIO

References: Illinois Adjutant General s Report 1900: Volume 8, page 549
Illinois Archives also gives this information:

Name SOMERS, SANDER A
Rank PVT Company I Unit 16 IL US CAV

Personal Characteristics
Residence:BLOOMINGTON, MCLEAN CO, IL
Age 19 Height 5' 8 Hair BROWN
Eyes HAZEL Complexion DARK Marital Status SINGLE Occupation FARMER
Nativity NASHVILLE, WASHINGTON CO, IL

Service Record
Joined When JAN 10, 1863 Joined Where MATTOON, IL
Joined By Whom JOHN MCKINSTRY Period 3 YRS
Muster In JAN 21, 1863 Muster In Where SPRINGFIELD, IL
Muster In By Whom N/A Muster Out AUG 19, 1865
Muster Out Where NASHVILLE, TN Muster Out By Whom CPT CHICKERING
Remarks: WAS PRISONER OF WAR

After the war he continued to suffer from the effects of the maladies that he suffered from in prison. He contracted rickets and scurvy while at Andersonville Prison.

Sanders Married Elizabeth Markham on 17 Jan 1866. She was born 1843/1844 Tennessee or Arkansas and died 21 Sept 1916 and is also buried in the I.O.O.F at Ashley. She was the daughter of Lewis Markham. Elizabeth and Sanders had 3 children: Florence Georgia, Etta Belle and Eva or Evie Summers.
According to Helen Smith Lamar (Granddaughter of Sanders Summers, 1999) "He was a frail man all his life and suffered so. He seems to have passed these problems on to his children as they all were frail , including my mother Etta Belle Summers Smith"


Sources for Sanders Summers:
Jerry and Frieda Lamar
Marci Lamar Kasen