Hi,
I think your grandparents birthdates are a little out. This is what I've found:
1851 Census Class Ho107/2418/456/14
Isabella Graham age 35 b.Cambois agricul.Labourer's wife
Christopher Graham 13
Amy Graham 4
John Graham (
George Graham 4
Robert Graham 6
All born cambois, Bedlington - living in Cambois- from a tree on A* Isabella's maiden name was probably Turner
1861 Census RG9/3873/42
George Graham b abt.1812 Heddon-on-the-Wall Ag. Lab 49
Isabella Graham 45
Christopher Graham 23
Ann Graham 21
George Graham 14
Robert Graham 11
1871 Census 1 Link House, Cambois, Bedlington
George Graham 63 Husbandsman
George Graham 24 Miner
Robert Graham 21 Miner
Ann Cambell 73 Housekeeper
Eliz Cheston 15 Housemaid
Isabella died 1862
1881 Census RG11/5115/25
Glebe Farm Bedlington
George Graham 73 Widower Ag. Lab
Relation: Father-in-law
Head William Hinckley 52
Ann Hinckley 41
Isabella M Hinckley 17
John Hinkley 15
Elizabeth A Hinckley 13
Geo. R. Hinckley 11
1881 Census RG11/5090/54/8
95 Foremans Row, Seaton Delaval
Head John Graham 38 b. Cambois, Miner
Isabella wife 34
William 11,
Christopher 9,
Robert 7,
Isabella Ann 6,
Margaret H 4,
Matthew 3,
thomas 1
1891 - same address
John head
Isabella
William 21 Miner
Christopher 19 Miner
Robert 17 Labourer Pit Heap
Margaret 14
Thomas 11
Elizabeth 9
Matthew 5 (probably the first Matthew had died)
1901 Census RG13/4809/163/33 Foremans Row, Seaton Delaval
John Head 58 Coal Hewer
Isabella 56
Christopher 2i9
Margaret 24
Thomas 21
Elizabeth 17
Matthew 15
Not so lucky with the McMillans
1901 Census RG13/4809/156/20
19 Foremans Row Seaton Delaval
James 41 b.abt 1860 Scotland, Coal Hewer
Isabella wife 36 b. Seaton Delaval
Mary Jane 16
John 14
Isabella 12
Elizabeth 9
Maggie 6
James 2
Hope this helps
Patricia