The 1840 U.S. Census has Dennis Smith (the father of Dennis M. Smith Jr.) in Holden, age 30 to 39. Other household members are one female age 30 to 39 (this would be his wife), one male under age 5, one male age 5 to 9, one male age 10 to 14, and one female age 10 to 14. See "United States Census, 1840," database with images, FamilySearch (https://www.familysearch.org/ark:/61903/1:1:XHT6-B99 : 8 December 2020), Dennis Smith, Holden, Worcester, Massachusetts, United States; citing p. 97, NARA microfilm publication , (Washington D.C.: National Archives and Records Administration, n.d.), roll ; FHL microfilm.
Marriage of Alice Jane Smith, daughter of John and Esther, on 19 June 1850: "Massachusetts State Vital Records, 1841-1920", database with images, FamilySearch (https://www.familysearch.org/ark:/61903/1:1:NW1L-VWX : 16 November 2022), Dennis Smith in entry for George W Mason and Alice Jane Smith, 1850.