Comborna,
The 1841 Census (ref.HO107 - 568 - 19 - 46 - 25) and 1851 Census (ref.HO107 - 2187 - 583 - 18) shows your Aaron as married to an Ann - no children. As with 1861 Census (which you appear to have) he is shown as born Toxteth Park, Liverpool and birth ca.1815/1816.
His baptism is listed as Aaron Stunstall bp.26/3/1815 St. Nicholas, Liverpool, son of Aaron and Dolly (familysearch).
Aaron Tunstall married Dorothy Booth 13/11/1798 Upholland (familysearch)
1st marriage for your Aaron Tunstall was to Ann Clark 9/3/1835 St. James, Liverpool (his christian name given as 'Heron' - familysearch).
So your Aaron Tunstall - engineer - is not connected to the Aaron on this thread who was a potter.
Annette