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What was Donald's occupation according to Mary's death certificate? If he was a tailor then this looks like the family in 1841 and 1851:
1841
Polintan, Ardnamurchan, Inverness
Donald Mceachen, 50, born Inverness, Tailor
Flora Mceachen, 40, born Inverness
Angus Mceachen, 25, born Inverness
Batchie Mceachen, 15, born Inverness (Ancestry transcription

probably Rachel, as in the 1851 census)
Lewis Mceachen, 10, born Inverness
1851
23 Boundaries of Way, Ardnamurchan, Inverness
Donald MacEachen, 62, Head, born Ardnamurchan, Inverness, Tailor
Flora MacEachen, 60, Wife, born Ardnamurchan, Inverness
Lewis MacEachen, 22, Son, born Ardnamurchan, Inverness, Fisher
Rachel Mceachen, 24, Daughter, born Ardnamurchan, Inverness, General Servant
Isabella Mceachen, 26, Daughter, born Ardnamurchan, Inverness, Herring Fisher's Wife
It looks like both Donald and Flora lived into the Statutory Register period and so their death certificates should give you the names of their parents and allow you to go back another generation on both sides
All the best,
Sarah