I am researching the McNaughtons of the Breadalabane area of Scotland. Alexander McNaughton - born on Lochtayside - was a doctor in the Royal Navy before settling in the Glengarry area. He married a Helen Grant and one of their sons was Alpin Grant McNaughton. I wonder if there is some connection to your ancestor Alpin Grant? I don't know any more about Alpin Grant McNaughton but his elder brother was also a doctor but died young.