Jemima was my great great great grandmother. Her maiden name of Aver was on James' birth certificate. I posted a copy of it on ancestry. I am descended from her youngest son Samson.
Jemima was jailed in Bodmin for smashing the windows in Truro workhouse. On her release she is described as 5 foot 3, brown hair, grey eyes and walks with a limp. I have not found any evidence of a marriage although Samson claimed to be the son of James when he got married. Samson had 21 convictions, mainly for poaching (and 21 children) There is an interesting story about him on line when he and James got drunk and had a falling out. James was tried at Northampton for trying to kill him , first by cutting his throat with a penknife and then shooting him. He was found not guilty as apparently the brothers were well known for fighting. The transcript is really funny in places.
My grandmother knew many of Samson's children, although her own father Samson died in his early twenties. He was a stone mason and he died of pneumosilicosis.
There is much about Jemima that remains a mystery and I have pretty much reached a dead end with it. One question is why James was baptised at Southam in Warwickshire where I can't find any connections at all.