Cyrus Vance was born on March 27, 1917, in Clarksburg, West Virginia. He was the son of John Carl Vance II and his wife Amy Roberts Vance, and had an elder brother, John Carl Vance III. Following Vance's birth, his family relocated to Bronxville, New York, so that his father could commute to New York City, where he was an insurance broker. Vance's father was also a landowner and worked for a government agency during World War I. He died unexpectedly of pneumonia in 1922. Vance's mother was Amy Roberts Vance, who had a prominent family history in Philadelphia and was active in civic affairs. Following her husband's death, she moved her family to Switzerland for a year, where Vance and his brother learned French at L'Institut Sillig in Vevey. Vance's much older cousin (referred to as an "uncle" within the family) John W. Davis, an Ambassador to the United Kingdom and 1924 United States presidential candidate, became his mentor and adopted him.