Hi, coming late to the discussion.
Archibald Black and Janet McChannich or Buchanan are my 3rd great grandparents.
I believe their children were Duncan (1785 Kilmodan) Mary (1787 Kilmodan) John (1789 Kilmodan) Jean/Jane (1791 Kilmodan) John (1793 Kilmodan) Janet (1795 Kilmodan) Walter (1797 Kilmodan) Archibald (1799 Kilmodan) and Niel (1804 Kilmodan). I have the OPRs from Scotland's people for all of these children (the spellings of Janet's surname do vary somewhat).
Janet herself I believe may have been born in Kilmodan in 1761, the daughter of Duncan McChannich and Jane or Jean Smith. If this is correct, she also has two sisters Margaret (1762 Kilmodan) and Jean (1767 Kilmodan). Again the OPRs are available on Scotland's People.
Archibald is more problematic, but I believe he has a brother named John who married Isabel McIntosh. The reason I believe these two are brothers is that the Black gravestones in Kilmodan are in a group of four similar stones, grouped together within a small fenced in enclosure. Two of the stones are badly eroded but one still clearly has Janet Buchanan, whilst the other has John Black and (just visible) Isabel McIntosh. The two other, much less eroded stones have members of Archibald and Janet's family, whilst the other has John and Isabel's descendants.
A further clue may be that just in front of the group a very badly eroded stone appears to say "The burial place of Archibald Black and Elizabeth..." There are OPRs of two children born to Archibald Black and Elizabeth Smith, Duncan born in 1765 and an unnamed child in 1772. Perhaps John and Archibald are also sons of Archibald and Elizabeth, but if so I can find no confirmation on Scotland's People.
@Sapienta Inverchaolin, Kilmodan, Glendaruel and Cowal are all close together, indeed the whole peninsula is known as the Cowal Peninsula. I have not found any marriage for Archibald and Janet McChannich, so I would be interested in where that comes from.