Robert Thin was the youngest surviving son of James Thin, the founder of 'James Thin, Booksellers'. Born in Edinburgh and educated at the Royal High School, he continued his education at the University of Edinburgh, graduating with an MA in 1883 and an MB, CM in 1887. After graduation he acted first as House Surgeon to Professor John Chiene and then House Physician to Dr John Wylie in the Royal Infirmary of Edinburgh and then as a resident in the Royal Hospital for Sick Children of Edinburgh. Thereafter he spent some months in postgraduate study in Berlin, Prague and Vienna, chiefly improving his knowledge of ear, nose and throat conditions and of midwifery. He became an assistant in general practice with Dr George Hunter of Linlithgow. At this time the railway bridge across the Forth was being built and one of his appointments was 'Assistant Medical Officer, Forth Bridge Works'.