Franklin's father's uncle was Herbert Samuel (later Viscount Samuel), who was the Home Secretary in 1916 and the first practising Jew to serve in the British Cabinet. Her aunt, Helen Caroline Franklin, known in the family as Mamie, was married to Norman de Mattos Bentwich, who was the Attorney General in the British Mandate of Palestine. Helen was active in trade union organisation and the women's suffrage movement and was later a member of the London County Council. Franklin's uncle, Hugh Franklin, was another prominent figure in the suffrage movement, although his actions therein embarrassed the Franklin family. Rosalind's middle name, "Elsie", was in memory of Hugh's first wife, who died in the 1918 flu pandemic. Her family was actively involved with the Working Men's College, where her father taught the subjects of electricity, magnetism, and the history of the Great War in the evenings, later becoming the vice-principal.