His baptism on FamilySearch:

parents: Thomas Seal,​ Mary Seal

name: James Seal
gender: Male
baptism/christening date: 05 Jan 1800
baptism/christening place: Parish of Chippenham, Co. of Cambridge, England
father's name: Thomas Seal
mother's name: Mary Seal
indexing project (batch) number: C03851-2
system origin: England-EASy
source film number: 887401
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The possible children baptised in or after their marriage year and all with parents of James and Elizabeth are:

First Last Birth Baptism Father's Mother's    Baptism
name(s)   name year year first name first name  place

Mary Seale 1823 1823 James Elizabeth  Soham
James Scale 1828 1828 James Elizabeth  Soham
Christopher Seale 1832 1832 James Elizabeth  Soham
Lydia Seale 1836 1836 James Elizabeth  Soham
Henry Seal 1840 1840 James Elizabeth  Soham
Benjamin Seal 1843 1843 James Elizabeth  Soham

The burials of those born from 1820 to 1860 are:

First name(s) Last name Birth year Death year  Burial year  Parish

Thomas Seale 1826 1826     1826        Soham
Thomas Scale 1826 1826     1826        Soham
James Seale 1828 1853     1853        Soham
Benjamin Seal 1843 1844     1844        Soham

Notice that Thomas has both Scale and Seale spellings, probably a mistrancription; further, of course, there is no record of his birth, possibly because he died before baptism.

The above burials explain why James did not appear after the 1951 census and Benjamin appeared in no census.  But Mary is a slight mystery: she may have left home early to get married or go into service she would have been 17 at the time of the 1841 census.  
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In 1841 census his family was:

Mill Corner, Soham, Newmarket, Cambridgeshire

First name(s) Last name Sex Age Birth year Occ  Birth place

James Seal Male 40 1801 Ag Lab Cambridgeshire
Elizabeth Seal Female 40 1801 Cambridgeshire
James Seal Male 12 1829 Cambridgeshire
Christopher Seal Male 8 1833 Cambridgeshire
Lydia Seal Female 5 1836 Cambridgeshire
Henry Seal Male 1 1840 Cambridgeshire

Archive reference HO107
Piece number 73
Book number 15
Folio number -
Page number 22

  HO107, piece 14, Book 15, p. 22
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By 1851 his wife had died and son Christopher had moved on:

Mill Corner, Soham, Newmarket, Cambridgeshire

First name(s) Last name Relationship Marital status  Sex  Age  Birth year  Occupation  Birth place
James Seal Head Widower Male 51 1800 Ag Lab Chippenham, Cambridgeshire
James Seal Son Unmarried Male 22 1829 Ag Lab Soham, Cambridgeshire
Lydia Seal Daughter - Female 14 1837 Domestic Duty  Soham, Cambridgeshire
Henry Seal Son - Male 10 1841 Field Work Soham, Cambridgeshire

Archive reference HO107 [sic]
Piece number 1763
Folio 216
Page 17

  Ref: HO107, piece 1763, folio 216, p. 17
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In 1861 Lydia and Henry were still with him and also there was a grandson James:

Water Side, Soham, Newmarket, Cambridgeshire

First name(s) Last name Relationship Marital status  Sex  Age  Birth year  Occupation  Birth place

James Seal Head Widower Male 60 1801 Agricultural Labourer  Chippenham, Cambridgeshire
Lydia Seal Daughter Unmarried Female 24 1837 Sempstress  Soham, Cambridgeshire
Henry Seal Son Unmarried Male 20 1841 Shoemaker  Soham, Cambridgeshire
James Seal Grandson - Male 7 1854 Scholar Soham, Cambridgeshire

Archive reference RG09
Piece number 1035
Folio 110
Page 19

  Ref: RG09, piece 1035, folio 110, p. 19
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His death cannot be found.  There was a James Seale who died in 1853 in the Newmarket Union but he was reported as only 25 years old, so not him!
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While this marriage is a little early, they could have had their first births dying early:

First name(s) James
Last name Seale
Marriage year 1823
Marriage date 22 Jun 1823
Marriage place Soham
Spouse's first name(s) Elizabeth
Spouse's last name Banyard
County Cambridgeshire
Country England
Record set England Marriages 1538-1973
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