The thing is, Robert had an accent, not too dissimilar to an Indian/Burmese. I had heard him speak what I took to be Hindi on a couple of occasions.
Just a comment here.
Knowing what I do of the speech and language development in children, I would say if his spoken English was accented, it was because his
first learnt and used language was
not English.
Perhaps it was Hindi as you suggest
The sounds needed for the first (primary) language are acquired and retained in the very early years. The second language, (in this case English) acquired later, may have imperfections of sound which create ”accent”
I would suggest that the SEALE couple were English-speaking. That should therefore be his first language. Not Hindi.
So have yet another inconsistency in the stories.
Sue