Hi, I don't know much about Pictou Co even though I have ancestry ties there so I looked up Big Brook -- "this rural area is located about halfway between Middle River and West Branch, East River on the line of the Canadian National Railway. The name was changed to Lorne by the inhabitants on Sept 30, 1878 in honour of the Governor General -- the Marquis of Lorne. Settlement began before 1789 by Robert, Alexander and William Dunbar and James Cameron."

I was thinking that the original settlers may be ancestors to your Donald Cameron and Elizabeth Dunbar.