Briefly - here is what I have with respect to the McKains - working backwards from me.
Ian M. F. Arnold - (1943 - Father - John Porteous Arnold (1910 - 1999) Grandfather - William Shaw Arnold (1877 - 1932) G Grandfather - John Porteous Arnold (1841 - 1926) (brought his family to Canada from Scotland) GG Grandfather - James Arnold (d 1869) GGG Grandfather - Thomas Arnold (d 1844) Thomas Arnold was married to Mary McKain. Her father. James McKain, was presented with a suffbox about 1816 for his role in helping Edinburgh survive a possible famine occasioned by a wheat shortage.
Hope this fills in a gap or two - does anyone know where James McKain fits in the overall family picture ?