Thomas Albert Cromwell was born on May 5, 1952, in Kingston, Ontario. His father, Ed Cromwell, owned Cromwell's Appliances on Brock Street in Kingston, a local landmark until Ed retired in 1985. Ed was also a musician who played drums for the Limestone City Jazz Band, suggesting that the younger Cromwell grew up in a household where music was a central part of family life. Thomas married Della Stanley on June 6, 1980, in Kingston; together they have one son, Tom Cromwell.