Hello John
I have just recently read your post. I don’t know if you now have a copy of the 1974 death certificate for James Muir. I see that it gives his marital status as “single”.
I wonder if “Aunty Flora” was a family friend (or connected to the Muir family in some way) but not actually Jimmy Muir’s aunt?
I think the name of the person who has signed James Muir’s death certificate is Douglas Kerr , who has signed as a “friend”.
I will email some other details to you.
Best wishes
Joan Findlay