Boy, talk about research, you should be a detective.I was put in contact with a woman who was writing about the Sparlings and she dug up most of the information for me, which, in turn, solved the mystery of two family lines she was working on. I'll send you the few more details I have about the family if a few days.
There is one thing that you may be able to help me find out.Marcus' youngest son, Omar Archibald (born in London, England), became an amateur fighter in England, I believe.He is supposed to have killed his best friend in the ring and emigrated to America with his wife Veronica Lynch, b. in Ireland, to escape prosecution.In this country he appears to have gone by Archibald.He eventually deserted his wife and three children, Veronica became mentally ill, the children were brought up in orphanages, and Veronica died in an insane asylum. It is not a pretty story.
Yes, by all means, please mention Marcus in your book.I have a feeling that he did a lot more for Roger Fenton than he was given credit for and deserves more recognition for his efforts.