The only safe way to proceed is to get a birth cert for one of the children, and then the marriage certificate.
You may wish to make a note of the following, to assess against the information you get from the certificates.
If - and it is a big if - Horton can be read as Norton, then the following entries may be worth considering:
HO107/1915 folio 91
1851 census, Bedminster, Bristol
East St
George Daw, Head, Married, 35, Tanner, born Norton Fitzwarren, Somerset
Sarah do, wife, 30, born do
James do, brother, Unmarried, 20, Labourer, born do
The 1841 census does not give relationships, and the ages of adults are meant to be rounded down to the nearest five years.
1841 Census HO107/959/14/10 p 14
Somerset, Taunton, Norton Fitzwarren
Norton Street
William Daw, 45, Ag Lab [Agricultural Labourer] Y[es born in county]
Martha 45 Y
Geo 25 Y
Charles 17 Y
James 11 Y
Louisa 6 Y
In the next household, same building:
Martha Barthomlow [?] 70 Pauper Y
In case this turn out to be the right family, you may find the following site of interest:
http://www.genuki.org.uk/big/eng/SOM/NortonFitzwarren/index.html