Jeanne (and Catherine),
I think we are 2nd cousins - I'm the granddaughter of James Ross and Margarite Dewar's brother 'Jack' (John Raymond McLagan) b 28 Jan 1894 in Glasgow, d 14 Feb 1972 in Dunoon.
My father (also John Raymond MacLagan Dewar), an only son b 1 Jan 1926 is still alive and remembers some of his uncles and some family stories - eg that they were part of the 'Dewar Quartet'.
I have been doing some family tree research and may be able to add more detail to what you've discovered - if you reply to this thread I should get notified and will take out a membership so we can get in touch (or let me know an email).
Rose (Rosemary) Dewar, Scotland