That’s what I suspected…..
John Simpson doesn’t seem to be around on the 1901 census - but I can’t find a death that fits.
He married Mary Harwood at Greasley – 22nd July 1875
Hopefully someone else will have another look and give their opinion.
Below is some of the findings when I was trying to find the right family so please excuse the ramblings…

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All I can offer are guesses and assumptions really….
The villages of Greasley, Kimberley, Newthorpe, Eastwood are all really close.
Is he the John born Greasley who is on the 1861, parents Samuel & Sarah?
1861 - RG9/ 2434/ 63/ 18 – Kimberley, Nottinghamshire
He marries Mary Harwood at Greasley – 22nd July 1875
On the 1881 census they are living next door to the Harwood family in Newthorpe
RG11/ 3322/ 77/ 39 – Club Row, Greasley
Children =
Frances E born abt 1876 in Newthorpe
Eliza A born abt 1878 in North Wingfield, Derbyshire
Arthur born abt 1881 in North Wingfield, Derbyshire.
1891 - RG12/ 2660/ 113/ 69 – Hill Top Common, Greasley, Nottinghamshire.
John Simpson, aged 39, Boot & Shoe Dealer, born Kimberley
Mary Simpson, aged 33, born Greasley
Samuel aged 8
Martha aged 6
Maud aged 2
Edmund aged 4 mths – children all born Greasley
William Harwood, aged 56 – Brother in Law born Greasley
By the 1901 census John has disappeared and Mary is remarried to Harry Stokes
1901 - RG13/ 3156/ 142/ 37 – Hucknall Torkard, Nottinghamshire.
Harry Stokes aged 35 born Tempsford, Bedfordshire
Mary Stokes 38 - born Eastwood
Sam Simpson 18 - born Eastwood
Maud Simpson 11 - born Eastwood
Nelly Stokes 4 - Hucknall Torkard
Harry Stokes 2 - born Hucknall Torkard
I haven’t found a death for John Simpson or a marriage for Harry/Henry Stokes to Mary Simpson
The son Edmund on the 1891 census appears to have been the one registered at Basford R/D
Births MarchQ 1891
Simpson Edmund Wallis Basford 7b 111
I can’t see the details from the 1911 census but he is in the same household as the Stokes family and John Harwood is also there.
I am sorry it gives no answer to what happened to John Simpson
On first look you must be thinking this is not the correct family as children seem to disappear from one census and new ones turn up on later census.
I did wonder if Edmund is the Edw’d on the 1901 RG13/ 3156/ 142/ 38 – born abt 1892 in Eastwood, but he is described as Adopted by Wm & Ellen Severn – but he is in Hucknall Torkard where Mary is living.
The Frances E Simpson on the 1881….on the 1891 census she is a servant in St Mary’s Nottingham