which younger daughter of Richard Nixon was Tricia Nixon Cox also a sister too 
Tricia Nixon Cox: Patricia "Tricia" Nixon Cox (born February 21, 1946) is the elder daughter of the 37th U.S. President Richard M. Nixon and First Lady Pat Nixon, and sister to Julie Nixon Eisenhower. Julie Nixon Eisenhower: Julie Nixon Eisenhower (born July 5, 1948) is the younger daughter of Richard Nixon, 37th President of the United States, and Pat Nixon, First Lady of the United States.
Julie Nixon Eisenhower