Henry (Harry) James Sinn was born in Werribee, Victoria, son of Charlie Edward Sinn, hotel keeper, and Mary Ann (nee Sexton), a farmer’s daughter. Harry was a popular gentleman of distinguished appearance with russet hair - turning silver in later years. He always dressed impeccably and had charming manners - exuding confidence to his patients, their families and his wide circle of friends. He died Melbourne aged 89 years.

He married Wilhelmina (Wilma) Marie Murphy, daughter of the prosperous couple, William and Anna Murphy, in 1936. Harry's and Wilma's marriage of sixty two years was described by their children as filled with family love, style and class. They had nine children: Bill, Andrew, Anna, Felicity, Stephen, Edward, Christopher, Mary Rose, and Catherine. There were also eighteen grandchildren and seven great grandchildren. Both Harry and Wilma were devout Catholics and two of their children entered religious life. The family were also devotees of the Carlton Football Club.

Harry Sinn was well regarded by his colleagues, in particular St Vincent's Hospital senior staff and the staff of the Royal Children's Hospital (RCH), then situated in Pelham St Carlton.

He was educated at St Kevin's College, Toorak and Newman College, graduating in medicine from the University of Melbourne in 1933. There were only 60 graduates in this Depression era group. After an appointment as JRMO at St Vincent's Hospital in 1934, he was appointed to RCH resident staff at Carlton in 1935 for paediatric training. in 1936, after their marriage, the couple voyaged by ship to the United Kingdom where he secured appointment as house physician at the Hospital for Sick Children Great Ormond Street, London. He gained his MRCP London in 1938.

On his return to Melbourne Harry took up appointment as clinical assistant at RCH and established rooms in 33 Collins Street. He practiced in consultant general medicine and his sub speciality of paediatrics. Senior appointments included Honorary Outpatient Physician at RCH from 1939 to 1960 and a similar appointment St Vincent's Hospital Melbourne (SVH) from 1939 to 1945. He took up honorary posts at SVH in 1960 as Physician to the Neonatal Unit and Senior Paediatric Physician in the newly-founded Department of Paediatrics.

Harry maintained the position of Senior Paediatric Physician at St Vincent's Hospital until his retirement in 1970. Later appointments included consultant to Vic Health from 1966 to 1982, assisting the preparation of annual government reports on paediatric morbidity and mortality. He also acted as consultant to National Mutual Insurance also from 1966 to 1982. In his final years he enjoyed consulting at the Mercy Hospital East Melbourne, sharing rooms with Mr Michael Somerville, gynaecologist, and Dr John McNamara, paediatrician.

Harry was elected FRACP in 1957. He regularly attended the annual scientific meetings of the College. He was also an early member of the Australian Paediatric Association and contributed to its annual meetings in Canberra at the Australian Academy of Science. He was president of the Paediatric Society of Victoria in 1962. This society, founded in the early 1900s, presented excellent monthly medical meetings for the paediatric community.

Harry Sinn was one of the early group of Australian physicians who aspired to a career in childhood medicine. His training combined paediatric and adult medicine in Melbourne and London. His MRCP preceded his MRACP. His Great Ormond Street appointment would have enhanced his paediatric experience but he had to practise general medicine, especially in the war years, to support his paediatric ambitions. His work load was considerable. He relinquished his Medical Outpatient Physician post at St Vincent's in 1945 to concentrate on paediatric consultation. He bridged the honorary/salaried consultant era and would not have received payment during his twenty years RCH appointment.

His family life was all important. Amongst his hobbies he enjoyed football, racing and gardening. His holiday home at Sorrento, the historic Anchorage (1882), was a special place providing relaxation for his large family and many friends.