Ian,
You have a great knack for finding these references - well done again. The notifications system on Rootschat doesn't seem to be consistently working otherwise I would have seen your post earlier (and the other recent posts from Bellam1 and Cathy which I now see that I also missed).
I tracked down the reference that you found in the Exeter Flying Post and realized that it was in turn an extract made from the London Gazette a couple of years earlier. Here is the original advertisement:
If John Brumwell and William Brumwell, who entered the merchant service as seamen, and went to sea in or about the year 1835, and who are the brothers and next of kin of Isabella Buckhall, widow, late of the parish of Walcot, in the county of Somerset, deceased, will apply at the office of Messrs. Cruttwell and Nicholson, 10, Godliman-street, Doctors’-commons, they may hear of something to their advantage. [The London Gazette, 27 September 1842, Issue 20145, p2610]
Clearly Isabella left her half-brother’s male offspring some money in her will. I assume John Brumwell must have died between 1835 and 1848 because I don't remember there being any reference to him in the 1848 admon of father William's will which you shared. The other piece of info to be gleaned from this announcement is that Richard and Isabella Buckoll had no living children in 1842 (if indeed they ever had any children).
Regards,
Jon