Where was Daniel in 1861 census? I expect he was in one of the logging camps north of Glengarry..... Some McMillan men of the 4th and 5th Lochiel Township were in Golden Lake at that time and some others were over the Ottawa River in Province of Quebec lumbering.
Isabella Cuthbert was born and raised on 3rd Lochiel. Do you know the parents of her mother, Catherine McMillan?