No, Eleanor was Theodore's niece by his brother Elliot.
Yes, Eleanor Roosevelt was the daughter of Elliot Roosevelt (b. 1860, d. 1894) by his wife Anna Rebecca (d. 1892), née Hall. Elliot Roosevelt was Theodore Roosevelt's younger brother.
No, Eleanor Roosevelt marred Franklin Delano Roosevelt. Theodore Roosevelt niece.
Theodore was Eleanor Roosevelt's uncle. Eleanor (full name Anna Eleanor Roosevelt) was the daughter of Theodore's brother Elliot.
He was her uncle, and also the fifth cousin of her husband Franklin Roosevelt.
Eleanor Roosevelt Biography
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Franklin Roosevelt Biography
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