Hui-lan Oei was the daughter of Chinese businessman Oei Tiong Ham. Her marriage to Chinese diplomat and politician Vi Kyuin Wellington Koo, was announced in November 1920 whilst Wellington Koo was Chinese Minister to the United States. In early 1921, Vi Kyuin Wellington Koo was appointed the Chinese Minister to Great Britain and they lived in London until June 1946, though they divorced shortly after the Second World War.