My wife's grandparents were Alexander Sampson McDonald and Patricia Martha Ferraday. According to family history (yes, I know that's not reliable) Alexander's parents were Allan McDonald and Elizabeth Donelda Lamont. Allan's parents were Alexander McDonald and Ann Cameron and this Alexander was a son of John McDonald, Sir John A's grandfather. Alexander and Ann are said to have emigrated to Canada in 1847. I've not made any real attempt to document anything earlier than her grandfather, but I suspect this is mostly true, which means she is descended from his uncle.