I an sure Keith Henthorn told you this story in good faith but I am sure that if you were to ask him to put any meat on the bones of this story he would be unable to do so.
The proof has not been found yet about the two brothers James and John, it is as simple as that.
Some of the most likely evidence actually points to the brothers being fairly wealthy so they would be unlikely to be looking for work in the traditional sense anyway. The idea of anyone going to Ireland to seek work seems unlikely anyway.
In fact now that I think about it I have been in touch with Keith several years ago and he kindly sent me some information about himself. At that time at least he was not doing any serious research into the Henthorn family
Don't worry I am 99% sure the information is there to be found it just needs someone with the time to look. I am retiring in 2025 and may have some time then but I hope to look make some time for a serious look before then LOL