You are no doubt going to think I am 'off my trolley' but please bear with me.
Looking at your other threads re. McKinnon I see that Neil was a shepherd, married to an Ann, and looking at a couple of the births of their children, they were said to have married 30/7/1883 and her maiden name was Paterson. Couldn't find a marriage for Neil Mckinnon and Ann Paterson 1883 so eventually searched for Ann Paterson married to a Mckinnon and up it popped BUT his name was shown as Donald, a shepherd, indeed married 30/7/1883 and his parents are indeed shown as Archibald McKinnon and Catherine McArthur (in census prior to marriage 'Donald' is listed as Neil, and a shepherd.
Again, from other threads, Catherine McKinnon was married to a James McDougall in 1866 and this also shows her parents as Archibald McKinnon and Catherine McArthur and her age suggests birthdate of 1839.
I firmly believe that Archibald McKinnon and Catherine McArthur who married 26/4/1831 Iona are indeed the parents of Catherine, and that 'Donald' and 'Neil' are actually the same person.
I believe that 1841 census you have of an Archibald, Catherine and a dau. Catherine 4 is NOT the right family - in 1841 Archibald and Cathrine are in Iona with Allan 5 (think this should read 8 years), John 5, Roger 3 (believe this is the Rory shown baptised 1837), and Cathrine 1. These children tie in with the baptisms that have already been listed on this thread. In 1851 still in Iona with further children Mary, Hugh, Thomas and Margaret. 'Donald' McKinnon is as you say with McArthur family and the 'Neil' you believe is yours is not the one with an Archibald and Christina (who you believe to be a second wife whom he married in 1849). Archibald married to Catherine McArthur is still alive in 1851! By 1861 - still in Iona - Catherine is now widowed, shown as Pauper, wid. of Ag. Lab.
As proved by marriage to Ann Paterson, and 1861/1871/1881 census, Donald McKinnon became Neil McKinnon as an adult (why I can't speculate), these are not 2 different people.
Archibald McKinnon died sometime between 1851 and 1861 and as I can't find a death for him from 1855 this would suggest that he died between 1851 and 1854 (which is of no help in confirming who his parents were). However, the 1851 census shows his birthplace as Kilfinichen bc.1803.
So, in conclusion, I can't confirm who his parents were, and I've no doubt muddied the waters somewhat - however, if the Catherine who married James McDougall and the 'Neil', shepherd, who married Ann Paterson (as Donald) are definitely 'yours' then the parents of both are definitely Archibald McKinnon and Catherine McArthur who lived in Iona 1841/1851/1861 (the latter with Catherine a widow).
I can't force you to believe me, of course, but feel sure I have got it correctly.
Annette