Hello...
No help sorry but I'm curious about a few things...
You wrote...
Mary Suisted (?Sjostedt) m John Smith << these are my research targets
Is the bit in brackets "(?Sjostedt)" your addition or was it written like that on their son's marriage certificate.
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It's a bit obvious but I'm guessing you've already looked through the 1861 and 1871 UK censuses for a five/fifteen year old John SMITH, son of John and Mary.
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Apart from their son's marriage certificate is there any other mention you've found of John and Mary SMITH
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Can I just clarify that you've made no actual connection between the adventurer guy Charles SUISTED and your Mary SUISTED. It's just a shared surname.
And out of interest, have you viewed the 1838 Denization Papers for Charles SUISTED.
http://discovery.nationalarchives.gov.uk/SearchUI/Details?uri=C9110487--
Happy to try and trace Mary SJÖSTEDT, sister of Charles SUISTED if you want. If this Mary stayed in Sweden it shouldn't be too hard to find her (famous last words

)
Regards
Beg