Are you still searching for your Wensley connection? I think this is the solution:
John Sully Wensley and Ann (nee Hall) had these children:
William & Margaret, born 1843 Bath, England;
Arthur Hall Wensley born 1844 London;
Caroline born 1847 Devon(?) England;
Susannah born 1852 Quebec;
Sarah born 1855 Canada.
William is listed as William John Wensley in the 1861 Quebec census, & is almost certainly your William Wensley.
Arthur, Caroline, Susie & Sarah had descendants in the USA.