Thomas was called by his nickname of "Grat" as well as "T.G.". He was one of four children born to John S. "Koester" (1794-1894) and Sussanna (Shoup). Their 4 children were:
John S., Thomas Gratton, Philip Theophilus and Barbara Ann.

Thomas moved with his family from PA to settle in Iowa; they later moved to Lowell, MO. Thomas eventually purchased the "Cunningham Place" in Sugarcreek, Arkansas, now known as Bella Vista, AR, where he was a blacksmith.

Thomas married Marilla Lee (Keller) on October 10, 1858 in Larksville, Luzerne Co, PA.
Their 11 children:
Mary Elnora, Clarisa Ellen, Charles, William LeRoy, Lily Myrtle, Minnie Louise, James Edwin, Susan Gertrude, Crissa Vida, Anna Violet and Bertha Maude
Thomas married his second wife, Catherine (McDonald), on May 2, 1898 in Newton Co, Missouri. No children were born to this union.
Thomas died on Saturday, July 31, 1915, at his home on Baxter St. in Neosho, MO, at the age of 78 years. His funeral service was held at the F.J. Bigham Undertaking Co. Chapel on Monday, August 2, 1915, at 2:30 p.m.

Neosho Times, August 5, 1915; page 1
DEATH OF T.G. CASTOR
T.G. Castor, one of the very old citizens of Neosho, best known as the manufacturer of "Last Chance" liniment, died last Saturday at his home in the north part of town, aged about 78 years. He had been in poor health for several months & his death was due to a general break down.
Mr. Castor was born in northeasthern Pennsylvavia but came west to Iowa about the time of the Civil War. He came to Neosho soon after the war & for many years he worked at the blacksmith trade. He was married twice & his second wife survives him. He leaves one son who lives in Harrison, ARk., & came up Monday to attend the funeral. Mr. Castor belonged to the Masonic Lodge & his funeral was conducted by that fraternity. He was a good citizen, honest in all his dealings & respected by all who knew him.