Hi Julie,
Thanks for your update. I remember your Grandad Tommy (with his quick wit and great sense of humour!) and your Grandma Peggy. I guess that your Dad is maybe Raymond, and that his older brothers are Alexander and Lachlan (may have that the wrong way round). I last saw Lachlan at my Mum's funeral in 2006, but haven't had any contact with either Raymond or Alexander since I was a young child (when we lived at Culzean for 1 year during 1956/7) due to a gardening job that your Grandma actually set up for my Dad! (She was on the catering side there, if I recall correctly - and your Grandad was a postman based in Maybole). Will have a think about other wider family members who might be much more knowledgable than me re the Hopetoun connection etc.
All the best,
Stuart