Are you suggesting that Lavinia was the wife of George's brother James born 1843 Stepney who disappears after the 1871 census.
I hadn't focused on this bit -- and indeed, it seems quite possible that James Stanley, of whom I can find no other trace, is James Sproston under a new name.
You are really placing too much store in formalities here -- people cohabited without marrying, people took on their partners' children without adopting them (which in fact was not possible before 1928 anyway), people changed their names when the whim took them (and women adopted the surnames of their partners), people added to or subtracted from their ages depending on their mood, or the ages of their partners, for instance.
Kind of as they do today!
Yes, James Stanley in 1891 was a good deal older than Lavinia Westgate -- it being far from uncommon at the time, as it had long been and still is, for older men to take up with younger women. But it could be a reason why, if he
was James Sproston, he minimized his age somewhat: making himself 42 rather than the 50 he really was (his birth was actually registered in 1840 in Stepney?).
And well whaddaya know: a James Sproston aged 59 died in Yarmouth in June quarter 1900.
He is a
perfect match for George's brother, and there he is dying
in Yarmouth.
So I think you solved that puzzle after all! James Stanley was James Sproston.
I eventually found why my gr-grfather changed his name, when another gr-grchild of his reported what his mother had known: that he took unilateral leave of the British military as a young man after five years in India rather than be sent to Afghanistan. The timing coincided perfectly with what I had figured out years before: he disappeared in 1873, and the Second Anglo-Afgan war started in 1878. So I had the reason for the name change, just not the reason for the name.
You need a reason for both James Sproston's name change and the name chosen. What we do have now is that we have identified Eva and Archibald, and have a good working hypothesis for how they came by the name Sproston:
Their father was James Sproston, going by the name James Stanley, and cohabiting with but not married to Lavinia Westgate.
Since the children all got the surname Stanley in their names, and apparently went by that surname, one wonders whether Lavinia was aware of the name shift on James's part before his death.