My Three Sons - Season 11 - Eps 13: St. Louis Blues
Katie's mother gives Katie and Robbie a vacation by taking the triplets to St. Louis with her for a couple of weeks. Robbie figures that now is the perfect time to do all of the things they haven't been able to do when they had the boys to look after.
About My Three Sons

Title: My Three Sons
First Air Date: 1960-09-29
Last Air Date: 1972-04-13
Status: Ended
Rating: 6.5/10 (from 33 votes)
Language: EN
Seasons: 12
Total Episodes: 380
Network: CBS
Genres: Comedy, Family
Production Companies: MCA Television, Don Fedderson Productions, Gregg-Don Inc.
Synopsis
A widower and aeronautical engineer named Steven Douglas raises three sons with the help of his father-in-law, and later the boys' great-uncle. An adopted son, a stepdaughter, wives, and another generation of sons join the loving family in later seasons.
Cast

Fred MacMurray
Steve Douglas

Don Grady
Robbie Douglas

Barry Livingston
Ernie Thompson

Stanley Livingston
Chip Douglas

William Demarest
Charley O'Casey

Beverly Garland
Barbara

Tina Cole
Katie

Dawn Lyn
Dodie Harper Douglas