Are you as confused as me? About the only constant things seem to be that William Mack Jr's father was William Mack and his mother was Marion.
William Mack and Jane Melrose's children seem to be following that conventional naming rule (if I have them all correct that is). First born is Barbara Melrose Mack, named precisely after mother's mother Barbara Melrose. Second born daughter is Marion Grieg Mack, presumably named after father's mother Marion Greig (which is a variant of mothers name listed on the death certificate). Third born daughter is named Janet Grieg Mack - wasn't the oldest daughter in the mothers family the next to be honored - and we do have an Aunt Janet Grieg named in the 1881 census. First born son is named William after father's father. So that pattern is holding.
But why Marion Cochrane? You might think this to be more accurate, as she was alive when William and Jane got married, but seems to be deceased as well by the time her son dies (am I reading that correctly?).
And what of that Greig family with the tempting surname of Henderson floating around (to match up with my Grandfather's brothers middle name). William McPool? He is Greig before and after the 1851 census, and McPool has to be a rare rare family name. He seems to be too old to be William Mack - his birth date is pretty consistent at around 1838, whereas William Mack seems to be born around 1845. Janet Greig looks to be the right age to be the Aunt Janet Greig however. I see that Euphemia and Hugh had several children, but I can't see a Marion among them however, which would have been convenient (give or take the Cochrane conundrum).
And why the constant fluctuation in family name between Grieg and Mack? I am getting the feeling that these people are anarchists, deliberately fouling up the government records!
Thanks for all this information by the way - the pics of those documents are wonderful to see.