Thomas was christened on June 30, 1850, three years before William. He was William's closest sibling in age and apparently William had a closer relationship with him than with his other siblings. In 1871, not long before William left for America, Thomas and William were living under the same roof.
Thomas married Hannah Illston in about 1874. Hannah was from Aylestone, Leicestershire, about 20 miles from West Haddon. Thomas and Hannah had ten children. Their family is a striking example of the poor health regulations in England in that era, as all of the children but one died by the year 1915. Thomas himself died in 1916, and Hannah in 1920. Two of the older children survived long enough to marry and have one child each, but their children also died at young ages. Thomas and his family wrote to the Clarks in America more often than the rest of William's family in England. The last letter we have from family in England is from Lois Clark Morley in December 1930. Lois was the only surviving child of Thomas Clarke, and her children were the only surviving grandchildren.