Here is William/Mark's parents' marriage:
St Paul
Bristol
Gloucestershire
23 April 1835
Joseph PREWET
Susan MINETT
https://beta.familysearch.org/1841 CensusThornbury
Gloucestershire
High Street
Joseph PREWETT, 28, Carter and Labourer
Susanna, 29
George, 4
Charles, 2
All born in the county
Next door,
possibly Joseph's parents:
(His parents are Thomas and Hannah)
James PREWETT, 54, Publican
Hestia (?), 54
Mark, 23
Charles, 21, Tailor
Emily, 18, Dressmaker (?)
Henry WALKER (?), 13
All born in the county
1851 CensusThornbury
Gloucestershire
High Street
Joseph PREWETT, 37, News Agent, born Alveston, Gloucestershire
Susan, 38
George, 13
Charles, 10
Charlotte, 7
Walter, 5
Henry, 2
All except Joseph born Thornbury.
James PREWETT, 66, Coach proprietor
Hester, wife, 66
Charles PREWETT, son, 32, Tailor
Mark PREWETT, grandson, 13, scholar
Hester WALKER, daughter, 46, widow, Needlewoman
Henry WALKER, grandson, 23, General Labourer
All born Thornbury
Mark born 1851:Sep Quarter 1851
PREWETT, Mark
Thornbury
Volume 11
Page 489
Susan died 1858:Sep Quarter 1858
PREWETT, Susan
Thornbury
Volume 6a
Page 105
Joseph remarried:Sep Quarter 1859
PREWETT, Joseph
WOOD, Emma Pavey
Bristol
Volume 6a
Page 30
http://freebmd.rootsweb.com/cgi/search.pl1861 CensusThornbury
Gloucestershire
High Street
Joseph PREWETT, 45, Ag. Lab., born Alveston, Gloucestershire
Emma, wife, 30, born Bristol
Henry, son, 11, Scholar
Mark, 9, ScholarEmma, 8 months
Children born Thornbury
This might be Mark/William, and perhaps the change of name was because he deserted:
1871 CensusList of the Officers, Men, Boys, Marines, and all other persons onboard Her majesty's Ship
Reserve on the night of Sunday, April 2nd, 1871
Mark PREWETT, Ordinary Seaman, 20, born Thornbury, Gloucestershire
He is noted as being on leave and the page is crossed out, clearly because they should not have been recorded if they were not there (some people just can't follow instructions!). I can't see him recorded elsewhere, but will have a look around and see if he is visiting family.
Here are his Navy service documents which you can download, and would be worth checking to see if there is mention of him deserting and perhaps confirm that this is the right person.
http://www.rootschat.com/links/0a8h/ Debra
