Thanks for adding to this thread. I will answer what I can. I also have 7 children for John M. and Alice. I don't know where the Brinkley name might have come from. Perhaps Alice had been previously married to a Brinkley. My wife's Great Aunt was George Roy Miller Sr's second wife.
I have an email from a Pat Abercrombie who states that Alice's father changed the family name from Abercrombie to Cole which was his mother's maiden name. This was done after 1880. Pat did not give me the name of Alice's parents and since this is a very peripheral line for me I had not checked any further. This name change might indicate that Alice's paternal grandfather was an Abercrombie but that there was a breakdown in the relationship between father and son.
You show Judy Lewis as wife of Horace Manson. I have Ruby from the 1920 census (death date 24 Mar 1931) and an infant Miller with a death date of 21 Apr 1926. The source of these dates is from a Richard Daake via email. The Miller line is his wife's ancestors.
I hope this is helpful. I wonder if there is any chance that your cousin's husband would know anything about when and where John Manson Miller, his grandfather, died. All I know is that he was still alive in 1935 but could not find him anywhere in the 1940 census.