Hi Jean,
Wow, thank you so much for the thorough analysis! Getting James' father wrong means that all my hypothetical tree prior to that is also wrong.
I notice the IGI has
7. FRANCIS NEAH SHIMMIN - International Genealogical Index
Gender: Male Christening: 12 OCT 1851 Saint Barnabas, Douglas, Isle Of Man,
England
I believed he was called Neal or Neil, as son of a MacNeil, so perhaps Neah is a mistranscription. It is odd that Jane MacNeil seems to have been born in Santon or St Anne. Might there be any reason for misrepresenting her origins? Presumably she died between 1861 and 1871 (unless she emigrated with her daughters?)
I have tried to find what happened to my great grandfather Frank's siblings. A Christian Shimmin married in the IoM in 1880, 1881 and 1882, but mine would be in her mid-thirties by then. None are recorded in IGI for Amelia.
There is a possible marriage for brother James in 1866 to Rebecca Cain in Braddan, but none for George. Walter may have married Annie Johnston in Braddan in 1876, but perhaps these Braddan marriages were a different Shimmin line.
Thanks again.
Desmond