Nicole,
I think I have found your family. David Wilson Brown was born at Outal on 3.11.1894 to John Brown & Ellen Buchanan. I have found them in the 1901 and 1911 censuses. I also looked up his sister Edith's birth to cross check it was the same family. So that's attached as well. David's father John died in 1941. And David died in 1964. David left a will which should be in PRONI (in paper format) if you wanted to read it. His father died intestate but there should still be a file with some information. If you go in person you can copy them yourself, free. (When PRONI re-opens of course).
The 1964 probate abstract says David died in Ballintoy. However there's no death certificate in Northern Ireland that matches that. But you said he was found on Islay. I couldn't find a death there but I did find one on Colonsay which is the next significant island north of Islay, so I'd say that's where his body was actually found. The Scotlandspeople site has a record of a death for David Wilson Brown aged 69 in 1964. Registered in Colonsay. GROS ref: 539/2 2. You can view that on the Scotlandspeople site if you register and buy some credits.
Scotlandspeople:
https://www.scotlandspeople.gov.uk/search-our-records
1901 census:
http://www.census.nationalarchives.ie/pages/1901/Antrim/Dundermott/Outal/928942/
1911:
http://www.census.nationalarchives.ie/pages/1911/Antrim/Dundermot/Outal/120143/
Brown, David of Outal Glarryford Ballymena county Antrim farmer died 15 September 1964 at Ballintoy county Antrim Probate Belfast 8 January to Thomas Gregg Buchanan farmer and George Hunter Boggs manufacturer. Effects £3783.
Brown John of Outal Glarryford county Antrim farmer died 14 July 1941 Administration Belfast 21 March to David Brown farmer. Effects £215.
Edith's birth:
https://civilrecords.irishgenealogy.ie/churchrecords/images/birth_returns/births_1901/01957/1755213.pdf
David Wilson Brown:
https://civilrecords.irishgenealogy.ie/churchrecords/images/birth_retur…