Christina Yvonne Cole (born August 4, 1943) is an American actress and singer. She is best known for her role as Katie Miller Douglas on the sitcom My Three Sons (1967–1972). She previously had a recurring role as Sunny Day in the detective series Hawaiian Eye (1963). She was also a member of the Four King Cousins, a subgroup of the King Family Singers. In 1963, she played the minor (uncredited) role of Ruth Stewart in Palm Springs Weekend, a spring break party film set in Palm Springs, California. She also appeared previously in My Three Sons as a friend of Robbie (circa 1966), cast in the role of Joanne, before the Katie role was created. She also was on the show as Sherry in the fifth season.