Chris - I have none of this family in my database but have just had a look at some Gulval PR information which brings up a couple of queries.
What is your source for the marriage of Richard Henry KESSELL to Margaret NANKERVIS??
And do you have any further information on the family that might help??
I will outline now what I have found that seems, in part, to match your Posting.
Gulval Marriages
9 Oct 1830 by Banns
Richard Kessell
Margaret Grenfell Jarman [mark]
Witnesses: Alice Tonkin, Richard Yale
Gulval Baptisms
11 Sep 1831 Elizabeth d/o Richard (labourer) and Margaret KESSELL of Trevaylor
27 Oct 1833 Mary Jane d/o Richard (labourer) and Margaret KESSELL of Trevaylor
13 Mar 1836 RICHARD HENRY s/o Richard (labourer) and Margaret KESSELL of Trevaylor
18 Nov 1838 Emily d/o Richard (gardener) and Margaret KESSELL of Trevaylor
04 Jul 1841 Priscilla d/o Richard (gardener) and Margaret KESSELL of Trevaylor
Gulval Burials
Richard Kessell of Trevallor aged 63, 16 Jan 1867
Later Gulval Marriages that may belong:-
20 Jan 1855 by Banns
William Jenkyns 29 Labourer of Gulval [mark] (Father: Martin Jenkyns, Miner)
Elizabeth Kessell 24 of Gulval (Father: Richard Kessell, Gardener)
Witnesses: Richard Kessell, Thomas Williams
27 Dec 1867 by Banns
Richard Hill 25 Farmer of Gulval (Father: William Hill, Labourer)
Priscilla Kessell 26 of Gulval (Father: Richard Kessell, Gardener)
Witnesses: John Carbis, Sarah Williams
1861 Census
Richard (57) gardener, wife Peggey (Margaret) (55) and daughter Priscilla (19) - all born Gulval - were living at Trevaylor
(Only a brief look but have not yet found son Richard Henry)
1851 Census, Trevaylor, Gulval
Richard Kessell, head, marr., 46, labourer on farm & gardens, bn. Gulval
Peggy Kessell, wife, marr., 47, bn. St Just
Elizabeth Kessell, daur, unm., 19, labourer, bn. Gulval
Richard Henry Kessell, son, unm., 15, apprentice to taylor, bn. Gulval
Emily Kessell, daur, unm., 12, scholar, bn. Gulval
Priscilla Kessell, daur, unm., 11, scholar, bn. Gulval
About the best I can do for the moment so will look forward to any further you can add that might help.
Happy to try and pursue the line back a little for you but let's deal with this bit first and work from there. (Think I might have a few more things to look at for you tonight.
)