?
Are we looking for military connections? as by 1881, James J DICKSON - age 23, born Bath, Somerset, is a Corporal in the Royal Marines, with wife Susan H DICKSON, age 21, born Hants, Alvestoke. Also as William DICKSON was a "Hatter' he could have been (as mad as a Hatter, from the Mercury used in the manufacturing process, this could explain the two wildly different places of birth)
'Mad as a Hatter'
http://www.cas.org/news/insights/science-connections/mad-hatter
On the 1861 John DICKSON says he was born in Wheathamstead, Hertford.
CLDS - Birth: John DICKSON, 15 October 1797 & Ancestry, born 17 September 1797 - parents: John & Catharine
Ancestry:
Marriage : Portsea Island, Hampshire - J/A/S qtr 1880
James John DICKSON and Susan Harriet CHILDS
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The above tree is on Public Members tree on Ancestry - with no parents of either couple. Only the marriage certificate would be able to help any further.
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re: 1861 census visiting John and Hannah DICKSON
Mary Ann HILLIER, Widow - 54 - born Glos Westbury on Severn
Gloucestershire Marriage Index
William HILLIER married Mary Ann CLARKE - Westbury on Severn - 12 July 1829
also on Fod Records (with no parents names given)
with witnesses: Cornelius CLARKE*** and Millicent CLARKE **
** Baptism at Westbury on Severn - 14 June 1807 - Millicent CLARKE, parents William & Sarah
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Mary Ann CLARKE's baptism at Westbury on Severn 29 September 1805 - parents William & Sarah. So it seems likely Hannah DICKSON is her sister.
***
Fod Records - Baptism at Westbury on Severn - 10 July 1796 - Cornelius CLARK - parents William & Sarah
Burial at Westbury on Severn - 16 November 1834, Cornelius CLARKE, residence: Eastington, age 38