Dear Alex, You must be "shell shocked" with a 300 year old history for the family in Scotland that you thought you would never find. Take heart and start with the Sonja Reid chart that Monica pointed us to. Start on the far left hand side of the chart with the one person you associate with. Each step to the right is "one generation" backwards in time. The number of people you have to think about raises to the power 2 at each step back. 1, 2, 4, 8, and then 16. I hardly think that another generation is on the cards but then again!
The Sonja Reid chart is of the same style as the *.PDF one I put up and they tell the same story although they were done by different persons working without the knowledge of the other. Incredible but they do agree on the main points of interest so you are on a winner.
I attach a few notes on Alex Reid b ~ 1765 and his family which will be useful when you get involved to that depth but that will take time and patience.
Best wishes, nw_whiskers