Very interesting (and reasssuring that your Dad didn't have 65 brothers as your first posting)!
Can you find out the names of your ggg grandad (who stayed in England) and his wife (who emigrated to US)?
If you have any ideas when she emigrated, we might find her on the emigration lists.
Also, can you name your gg grandad and any details about his date of birth/marriage/death - these will help place his origin in the UK?
Often, an old Family bible survives and in the faded pages, if you're lucky, your Family details emerge - I do hope so as it will prove a real gem to you - sometimes, these old Bibles are hidden away in the assets/lofts/personal effects of an elderly relative, unknown to the rest of the family, so do ask all your relations ... hope I'm not 'teaching grandmother to suck eggs' as they say in England!
My direct email is email@example.com - feel free to use that.