Can you name the two of our Church Presidents that were nephews to previous Church Presidents? (meaning that their uncles served as Church Presidents?)
 

President Joseph F. Smith, son of Hyrum Smith ~ the brother of the
Prophet Joseph Smith.

This means that Joseph F. Smith was the nephew of the Prophet Joseph.

President Spencer W. Kimball was the son of Andrew Kimball.
Andrew Kimball was the twin brother of Alice Kimball Smith, a wife of President
Joseph F. Smith. Thus, Spencer W. Kimball was a nephew of President Joseph
F. Smith.