OK - Grandson Martin here:
My father was born - Eric Michael Benjamin in 1905
His father was Edwin Hime Benjamin
[Now he disappears from all records after he went into hospital, but in the US, an Edwin Hume Benjamin turns up again - I think this is our man! I can't think why else they would go to the US and return soon afterwards unless he was over there!]
His mother was Charlotte Roberts (named as Benjamin on the birth certiificate)
To our knowledge (only what we have been told) he was an only child. But maybe not?
He did sail to New York as you say, and attended school there, it was a strict jewish school as he remembered having to wwear the traditional jewish clothes. He lived near 'Bennett Avenue' which obviously gave him the idea for the name change in 1947 from Benjamin to Bennett
He had a first wife - Dorothy Goggin
Who produced a son - David Bennett
And a daughter - Janet Bennett
He met and married my mother in 1951 - We are all Bennetts! No one has changed their names.
All of this has been shrouded in mystery and there seems to have been a lot of 'shameful' goings on.
My dad planned to go and live in Brazil and left for there days after his 21st birthday in '26. But he returned again to Britain, ultimately joining the RAF and becoming an officer for the duration of WW2. Serving as Eric Benjamin. Name changed to Bennett in 1947.
OK - Might help you guys a bit - But I dont know much more than you.
TTFN
Martin.