Graves was born into a middle-class family in
Wimbledon, then part of
Surrey, now part of
London. He was the third of five children born to
Alfred Perceval Graves (1846–1931), an
Irish school inspector,
Gaelic scholar and the author of the popular song "Father O'Flynn", and his second wife, Amalie von Ranke (1857–1951).
At the age of seven,
double pneumonia following
measles almost took Graves's life, the first of three occasions when he was despaired of by his doctors as a result of afflictions of the lungs, the second being the result of a war-wound (see below) and the third when he contracted
Spanish influenza in late 1918, immediately before
 At school, Graves was enrolled as Robert von Ranke Graves and in Germany his books are published under that name but before and during the First World War, the name caused him difficulties. In August 1916 an officer who disliked him spread the rumour that he was the brother of a captured German spy who had assumed the name "Carl Graves".
 The problem resurfaced in a minor way in the
Second World War, when a suspicious rural policeman blocked his appointment to the
 Graves's eldest half-brother,
Philip Perceval Graves, achieved note as a journalist and his younger brother,
Charles Patrick Graves, was a writer and journalist.