We traced to Archibald McLaren who came to Balderson Ont 1816 via the ship Fanny in 1816 (possibly 1818). His brother Peter came 1817 on the Prompt. They settled side by side just E of Balderson. I recently got copies of several letters to Peter from family and that gave me a Brother Donald, writing from Balnasuim 1821, 28 and 30. They also indicate the mother Isabella (writing as late as 1837 and still alive in 1849 per Catherine letters) and sister Catherine married to Peter McGregor. The 1841 census says Peter/Catherine are at Lawnacroy (but doesn't mention Isabella in that family) and that she is daughter of Isabella McGregor and Duncan McLaren
I don't know the James/Hugh combinations you write about.
Okay. I have fleshed out your tree.
Duncan McLaren and Isabel McGregor married 1788 and their first born Patrick/Peter was born at Crannich on the north shore of Loch Tay in Feb 1789. Their daughter Catherine was born at Skiag on the opposite shore in Oct 1789. Their son Archibald was likely born at Skiag as well. I am interested to hear more about whether they had additional children such as the Donald you mention. As for Catherine's incorrect death certificate with the wrong mother, this does occur in records. The recorder and/or children may list incorrect names. I do not have Peter McGregors parents identified yet - but maybe the Catherine Campbell comes from there.
Peter McLaren married Mary Sinclair of Rynachulig - just southwest of Crannich area. Went to Drummond, Lanark.
Archibald McLaren married Catherine McQuarrie of Ardeonaig. No birth record for her, but I believe her parents were Alexander McQuarrie and Catherine Campbell. I have not indexed the McQuarries yet, so I am not 100% on her origins yet.
Kori