Hello Annette,
Thank you so much.
Whilst it is likely that we will never know for sure, your reasoning makes a good deal of sense.
I spent many, many hours researching my wife's side of our family tree before turning my attention to mine and found that there were times when the balance of probability was all you could go on. We will never know for certain, but it is quite likely you are correct. Did Ester (Esther)raise Robert? He would have been 5 years old by the time she married John Frost. Quite possibly she did given her son John (b.1816) named one of his own children Robert presumably after his older half-brother. Interesting though he kept his mother's surname.
No, I only have the military researcher's report. The work was commissioned around 1992 or 1993 by Alan Banks, a cousin of my father. Alan is an old man now (91), but still quite sharp. Unfortunately he lives over the other side of the country from me, but I will make a point of visiting him again soon to see what he remembers and whether he has further details.
Thanks also for the information about what you are likely to find on the early military records. This sort of detail is invaluable to us amateurs - no point in going to a lot of trouble chasing down records if they reveal nothing new.
Thanks again,
Brendan