Harry Hopkins
Harry Lloyd Hopkins (17 August 1890 – 29 January 1946) was, during the Franklin Delano Roosevelt administration, one of the architects of the New Deal during Great Depression and of foreign policy involving WWII. He is stated to have been Roosevelt's chief diplomatic troubleshooter and liaison with Winston Churchill and Joseph Stalin. Before Hopkins began to decline from cancer, Roosevelt even appeared to be training him as a possible successor.
In 1913, Hopkins married Ethel Gross, a Hungarian-Jewish immigrant active in New York City's Progressive movement. He divorced her in 1930, but they had three sons and the two kept up an intimate correspondence until 1945.
There have been some claims that Hopkins was a Soviet agent, but even many revisionist sources on WWII do not support this. Regardless, his half-Jewish children may have been a personal reason for Hopkins to be hostile of National Socialist Germany and supportive of its enemies.