There’s conflicting information on which of Mercer Srs. two wives was Jrs. mother.
http://boards.ancestry.com/thread.aspx?mv=flat&m=335&p=surnames.fain
Mercer Fain (son of Mercer Fain and Martha Springfield) was born 1820, and died date unknown
http://familytreemaker.genealogy.com/users/k/i/n/Dana-Michelle-Kinsey-GA/WEBSITE-0001/UHP-0163.html
Born on 1820 to Mercer Fain and Louisa McLennan.
http://records.ancestry.com/Mercer_Fain_records.ashx?pid=120607473
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Research of Travis Joyce:
Mexican War
Mercer Fane, Jr., Third Corporal (Faine), Muster into federal service April 5, 1847-mustered out August 8, 1848. Middleton T. Johnson's Company (Captain). Composed of personnel recruited mainly from Shelby County, Texas.
(Second Service)
Mercer Faine, Jr., Pvt. Mustered into federal service August 8, 1848 (same day he mustered out of previous service), Mustered out of federal service Dec. 15, 1848. Joseph M. Smith's Company (Captain). Composed of personnel recruited primarily at Kaufman Station, Texas (have not determined where this is).
Mercer's brother, William, (by Mercer Sr. first wife) also enlisted on the same day and served in the same company with Mercer Jr.
These units were formed to protect the Texas border, and were not involved in any invasion activities in Mexico. They were both part of P. Hansbough Bell's Regiment of Texas Mounted volunteers.
Indian Wars (fighting Comanches)
Mercer Fain, 2nd Lt. and Acting Quartermaster, Texas Rangers Mounted Volunteers, Enlisted Nov. 1854 - ?.
Capt. John G. Walker
Company called out (again) by - Smith February 1856
On June 13, 1855, Mercer Fain Jr., signed over a power of attorney to a lawyer in San Antonio, Texas for him to get the money due Mercer from the Texas Treasury for the "service of my slaves and team while in the service of Captain John G. Walker and Captain William R. Henry." The museum furnish a copy of this paper, signed in San Antonio. As Acting Quartermaster, Mercer was obviously also furnishing the company his slaves, mules and wagons during their campaign against the Comanches in 1855.
http://wc.rootsweb.ancestry.com/cgi-bin/igm.cgi?op=GET&db=meyer465&id=I3002
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In Nov. 1861, Mercer Fain was the enrolling officer at Ft Arbuckle, Chickasaw Nation (now Oklahoma) who enrolled many members of Co. E, Chickasaw Battalion, which later became John J. Scanland's Company and later Co. A of Scanland's Squadron.
http://boards.ancestry.com/thread.aspx?mv=flat&m=335&p=surnames.fain
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Beef Contractors with the U. S. Army in Texas,1849-1860
1850
Mercer Fain Towash Village
http://books.google.com/books?id=phOIOnzTvv8C&pg=PA209&lpg=PA209&dq=Mercer+Fain+Texas&source=bl&ots=3p2tu6pP5S&sig=FMRZWP77NT68LAYGSRFdn5d27Ao&hl=en&sa=X&ei=snz9UtnKJdKCogSzoYEo&ved=0CDsQ6AEwAzgK#v=onepage&q=Mercer%20Fain%20Texas&f=false
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Do not know if this could be him in 1850
Moody Census Records 1850 (Western NC)
CHEROKEE CO, NC
Name Age S R Occupation Value Place of Birth
FAIN MERCER? 30 M W MERCHANT 2300 GA 1819/1820
http://www.martygrant.com/genealogy/moody/moody-1850.htm