I know it's been a while since you posted this but my grand fathers father was William F Callister and his wife was Ann J (nee Lang) Callister.
My grand fathers name was Fred (Frederick) and I know he had a brother George (as I met him around 1955 when he came over from Isle of Man to South Africa)- I have photo's of George's daughter, son in law, grand son and grand daughter. I know their last name was Bool.
Fred was born in Surrey, England and later moved to Isle of Man then eventually South Africa. I have managed to trace Ann back to Scotland.
Would love to hear from you.