Welcome to Rootschat, R C Steele! Maybe we can steer you onto the right path with a little more info added. (Important to know if there is a proven connection to the parents / location you've suggested for Thomas)
adding: reply to posts from amondg - Rosie's find isn't unusual (Plus this was the posted request) ...Once you've done this as often as we have, many outcomes are seen as possible. Grandmas giving birth to the uncles of her children's children. Found one gal from Scotland married as as she turned a teen, and gave birth to 16 live children in over 2 1/2 decades. My husband's ancestor was 70 when he fathered his last child with his generation younger second wife.
Wondering if those are the correct parents as marriages in that era didn't often have parents listed...I found a tree on Family Search but there is no proof of connection to the couple stated. Thomas & Margaret died in Manitoba, so may have found the info on the death cert. altho the database shows both parents as unknown, whereas it is usually left blank so you have to pay for the cert. They both did die in the RM of LANGFORD MB, where George Henderson Steele married in 1900. Also they found him in 1851 so he immigrated earlier.
https://www.familysearch.org/tree/pedigree/landscape/KC1Q-2CGThere may be a clue in that he worked as a carpenter as well as farmer...Also may be clues in the children's middle names: McKay, Henderson, .. They had twins so were the Steel or Dunn families likely to bear twins??? Their grandchild Matthew Bramwell Steele had fraternal twins.
also 1861 He says born 1825
Janet 7 William 5 Matthew 3 - listed as died at birth, but that must have been Thomas 1
https://recherche-collection-search.bac-lac.gc.ca/eng/Home/Record?app=census&IdNumber=455715171871 He says b. 1827
Thomas 4 John M 2 George 2
https://recherche-collection-search.bac-lac.gc.ca/eng/Home/Record?app=census&IdNumber=455715171881 says b. 1819 farmer & carpenter (scroll down)
https://recherche-collection-search.bac-lac.gc.ca/eng/Home/Record?app=census&IdNumber=19453767Thomas & Margaret - Noting that she's 43 with a 14 mo. old baby!!!
Jeanette 27 William D. 25 Maggie 16
Twins* John McKay Steel 12 George Henderson Steel 12
Archibald 9 Harry Steel 1
1891-Found them in Marquette Manitoba - but Margaret says she's a widow...Can't see him in 1891
https://recherche-collection-search.bac-lac.gc.ca/eng/Home/Record?app=census&IdNumber=24027518