Marvin Terrell (M. T.) Chamberlain was the eldest son of Lawson Watkins Chamberlain (1860-1947) and Susan Olive Frey (1860-1953). In 1906, he married Edna Caughran. The couple had nine children. Marvin served as Knox Co. clerk for many years. Sometime after Edna's death in 1953, he moved to San Antonio.