I hope this information will be of some help to the people who are interested in the General Thomas genealogy.
This is some information from _George Henry Thomas: The Dependable General_ by Frank A. Palumbo.
"George H. Thomas was born July 31, 1816 in Southampton County, Virginia. He was one of nine children born to John C. Thomas and Elizabeth, nee Rochelle. There were six girls and three boys. George was the youngest boy. His two brothers were named John William (eldest) and Benjamin and two of his sisters were named Judith Elvira and Francis G. Thomas. Benjamin later communicated with George after the war from his home in Vicksburg, MS.
His parents were married February 9, 1808 in Southampton County by Joseph Curley an Episcopal clergyman. The father died April 20, 1829 at the age of forty-five, the victim of a farm accident. George Thomas' paternal forbearers were Welsh and English, and his maternal ancestors were French Huguenot. His father's family, if originally Welsh, had lived in England for several generations before coming to America. Many members of the family died intestate, providing no clues in tracing their ancestral lineage."
From the stone at the Thomas family plot in Virginia the name of the nine children are: (note that Benjamin and George are not listed on the stone as they are buried elsewhere):
1. John William
2. Judith Elvira (died 1903 spinster)
3. Benjamin (1814-1876, buried at Vicksburg, Mississippi)
4. George Henry (born 31 July 1816, died in San Francisco 28 March 1870 and buried at Troy, NY)
6. Francis G. (Fanny, died 1902 spinster)
7. Lucy Briggs (nee Thomas)
Francis F. McKinney states in a footnote in his book _Education in Violence: The Life of George H. Thomas_ that "the details of the Thomas genealogy have been filed by the author with the Virginia State Library, Richmond". Perhaps you can find more information there.
On November 17, 1852, Thomas married Frances Lucretia Kellogg of Troy, New York at St. Paul's Episcopal Church in Troy. The church register indicates that the official witnesses were her brother John F. Kellogg and her uncle Daniel Southwick. Frances' mother, Mrs. Abigail Paine Kellogg had been a widow for many years. Her husband Warren Kellogg was a prosperous hardware and grocery merchant.
George H. Thomas had no children.
A WEB page with a lot of genealogy on the Thomas name is: http://www.genealogytoday.com/surname/finder.mv?Surname=Thomas
Some of the information on the Thomas family below may be in error: