Background: Sir Alexander Fleming  (6 August 1881 - 11 March 1955) was a Scottish physician, microbiologist, and pharmacologist. His best-known discoveries are the enzyme lysozyme in 1923 and the world's first antibiotic substance benzylpenicillin (Penicillin G) from the mould Penicillium notatum in 1928, for which he shared the Nobel Prize in Physiology or Medicine in 1945 with Howard Florey and Ernst Boris Chain. He wrote many articles on bacteriology, immunology, and chemotherapy. Fleming was knighted for his scientific achievements in 1944.
Context: Born on 6 August 1881 at Lochfield farm near Darvel, in Ayrshire, Scotland, Alexander was the third of the four children of farmer Hugh Fleming (1816-1888) from his second marriage to Grace Stirling Morton (1848-1928), the daughter of a neighbouring farmer. Hugh Fleming had four surviving children from his first marriage. He was 59 at the time of his second marriage, and died when Alexander was seven.  Fleming went to Loudoun Moor School and Darvel School, and earned a two-year scholarship to Kilmarnock Academy before moving to London, where he attended the Royal Polytechnic Institution. After working in a shipping office for four years, the twenty-year-old Alexander Fleming inherited some money from an uncle, John Fleming. His elder brother, Tom, was already a physician and suggested to him that he should follow the same career, and so in 1903, the younger Alexander enrolled at St Mary's Hospital Medical School in Paddington; he qualified with an MBBS degree from the school with distinction in 1906.  Fleming had been a private in the London Scottish Regiment of the Volunteer Force since 1900, and had been a member of the rifle club at the medical school. The captain of the club, wishing to retain Fleming in the team, suggested that he join the research department at St Mary's, where he became assistant bacteriologist to Sir Almroth Wright, a pioneer in vaccine therapy and immunology. In 1908, he gained a BSc degree with Gold Medal in Bacteriology, and became a lecturer at St Mary's until 1914. Fleming served throughout World War I as a captain in the Royal Army Medical Corps, and was mentioned in dispatches. He and many of his colleagues worked in battlefield hospitals at the Western Front in France. In 1918 he returned to St Mary's Hospital, where he was elected Professor of Bacteriology of the University of London in 1928. In 1951 he was elected the Rector of the University of Edinburgh for a term of three years.
Question: Who were his siblings?

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