He married Mary who was born about 1879 in Aberdare, Glamorganshire.
In the England and Wales Census, 1911, Thomas was age 31, an Engine Driver in a Tinplate Works. He was living in Aberdare with his wife Mary, son Thomas James (7),son David John (5), daughter Alice (3), and infant daughter Margaret Mary.
Census 1939
3 Phillip Street , Aberdare U.D., Glamorganshire, Wales
Thomas W Hart 15 Mar 1880 Male Tinwork Engineman & Stor Married
Mary Hart 20 May 1878 Female Unpaid Domestic Dutie Married
David J Hart 04 May 1905 Male Colliery Haulage Engineman Below Single
Richard W Hart ? Nov 1913 Male Porter Waiter Hotel Single
Thomas William Hart died in September of 1966, at the age of 86.
Sources
"England and Wales Census, 1881," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:Q2W9-9GG5 : 11 December 2017), Thomas Wm Hart in household of William Hart, Whitchurch, Glamorganshire, Wales; from "1881 England, Scotland and Wales Census," database and images, findmypast (http://www.findmypast.com : n.d.); citing p. 27, Piece/Folio 5275/166, The National Archives, Kew, Surrey; FHL microfilm 101,775,448. | Accessed 25 January 2022
"England and Wales Census, 1901," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:XSM8-S42 : 21 May 2019), Thomas Hart in household of William Thomas Hart, Aberdare, Glamorgan, Wales, United Kingdom; from "1901 England, Scotland and Wales census," database and images, findmypast (http://www.findmypast.com : n.d.); citing Aberdare subdistrict, PRO RG 13, The National Archives, Kew, Surrey. | Accessed 25 January 2022
"England and Wales Census, 1911," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:XWXH-QBD : 27 June 2019), Thomas William Hart, Aberdare, Glamorgan, Wales, United Kingdom; from "1911 England and Wales census," database and images, findmypast (http://www.findmypast.com : n.d.); citing PRO RG 14, The National Archives of the UK, Kew, Surrey. | Accessed 25 January 2022