Hi Justin
I do think it was Nesanelis > Brooks, rather than Brooks > Nesanelis.
Nesanelis being an unusual name even for the Ukraine. Its origins are more likely to be Lithuania according to Jewish name expert Alexander Baider (who someone kindly asked on my behalf on the JG Forum). Both Leon Saul and Simon Harry have a connection to the name Nesanelis and were brothers who found themselves in the UK in the late 19th century.
I've managed to track both brothers down from almost cradle to their final resting places - picking up on a newspaper trail, alien registers, and the more 'normal' route of my research i.e. census, electoral registers and BMD (including the Glasgow wedding). Leon's father is listed as Fayvel!
I've reached out on the JG forum as you suggested to see what others may think, and I'm hoping that the naturalisation records of Simon's wife (when I see them) may give some extra clues.
As for sources of information happy to share here - as I've found it incredibly useful on Rootschat to discover sources through other people's stories. So hoping this also proves useful....
For Ukrainian records there is a chap - Alex Krakovsky, from Kyiv I believe, who keeps taking the government to court re. access to historic records. He wins, copies and then publishes online what he finds. This is the translated index of his records:
https://translate.google.com/translate?sl=ru&tl=en&u=https://commons.wikimedia.org/w/index.php?title%3DSpecial:Search%26limit%3D500%26offset%3D0%26profile%3Ddefault%26search%3DAlexkrakovsky%26advancedSearch-current%3D%7B%7D%26ns0%3D1%26ns6%3D1%26ns12%3D1%26ns14%3D1%26ns100%3D1%26ns106%3D1Access is free but if you are like me and don't understand Russian you need to train your eyes for some key letters of the Russian alphabet! stevemorse.org is an excellent resource.
Another incredibly useful source of information for the Ukraine has been the database maintained by Nadia Lipes:
https://lipesdatabase.com/about/It's not cheap. But I've splashed out a few translated records, and the index which includes locations and the patronymics are also a useful pointer.
Some of the records I've been looking at go back to early 19th century Ukraine!
The Russian military records databases are more miss than hit - but I've also retrieved a few key documents:
https://gwar.mil.ru/heroes/?fbclid=IwAR13Hd4gt3McOLAJxu3ClvfCDDRhhXwTzsybxQTMlwsgOI5AzYmwDq97IKMFinally for me an unexpected source of information - the Hoover Institute in San Francisco.
It holds copies of the Okhrana Files that were produced or held by the Tsar's secret police in Paris.
Lots of photographs, copies of letters. Sadly there was no photo of my ancestors but they provided a copy of an intercepted letter that was addressed to my great * 3 grandfather.
I'm also looking at DNA matching as a means of filling in the gaps on the family line, and trying to track down descendants in the UK, though that is proving more difficult than I imagined. Though both Simon and Leon were from big families their own children didn't all go on themselves to have offspring.
best wishes
Neil