Thank you all.
William’s 1903 death record confirms my work from 2016 pointing to Alexander McKay / Mackay and Margaret Simpson being my 4th great grandparents. All I have been able to find on them is an 1806 marriage record (Culbokie, Ross and Cromarty), and the births / baptisms of William (1821) and Alexander Jr (1816), both in Knochbain.
I have tried locating death records for Alexander and Margaret, hoping that would tell me their parents. But I don’t know their ages (don’t appear in the marriage record). And I haven’t found them in any Census. I have spent many, many hours trying to find them in 1841, focusing on Ross and Cromarty (which was flooded with McKays), with a range of ages. Many Alexanders married to many Margarets, both with and without sons named William and Alexander, who might be on their own by 1841, but no luck so far pulling it all together.
I’m left wondering, with such common names and no years of birth, is this a hopeless search? Maybe someone who hasn’t been staring at these names for hours on end can see things more clearly?