<P> My Three Sons moved to the CBS television network for the 1965 - 1966 season after ABC declined to commit to underwriting the expense of producing the program in color . Along with the change in networks and the transition to color, Tim Considine (who had earlier worked with Fred MacMurray on The Shaggy Dog), playing eldest son Mike, had chosen not to renew his contract due to a clash with executive producer Don Fedderson over Considine's wish to direct but not co-star in the series . (Considine did, however, direct one of the last black - and - white episodes for ABC .) In an August 1989 interview on the Pat Sajak Show, he explained that he was also devoted to automobile racing, which his contract forbade . His character was written out, along with Meredith MacRae, who had played his fiancee Sally, in a wedding episode that was the premiere of the 1965--1966 season on CBS . After this episode, which was the program's first in color, Mike is mentioned briefly in only four succeeding episodes (including one in which Ernie becomes adopted), and is never seen again, even at Robbie and Steve's weddings . In the episode "Steve and the Huntress" (first aired January 27, 1966), Mike is specifically mentioned as teaching at a college . MacRae joined Petticoat Junction the following year, the last of three actresses to play Billie Jo Bradley . </P> <P> To keep the show's title plausible, the show's head writer, George Tibbles, fashioned a three - part story arc in which an orphaned friend of youngest brother Richard (Chip, played by Stanley Livingston), Ernie Thompson (played by his real - life brother, Barry Livingston), awaits adoption when his current foster parents are transferred to the Orient . Steve offers to adopt Ernie, but faces antagonism from Uncle Charley, who finds Ernie a bit grating, and forecasts major headaches over both the boy and his dog . It also transpires that a law requires a woman to live in the home of an adoptive family . A likable female social worker supervises the case, and the Douglases speculate that Steve might marry the woman, to make the adoption possible, but they both agree this is not reason enough for them to be married . The family also does not need to hire a housekeeper, since Uncle Charley already has things running smoothly . The family soon appears before a judge who researches the law, and determines that its intent is to ensure a full - time caregiver is in the household . With Charley meeting that role, and having had a change of heart about Ernie, Charley assents to a legal fiction declaring him "housemother" to the Douglas family . </P> <P> While the three sons were always central to the storyline, several major changes took place by the late 1960s . In the spring of 1967, the ratings for the series began to sag and My Three Sons finished its seventh season in 31st place in the Nielsen ratings . It was decided that the 1967 - 1968 season would bring the program not only a new time slot, but also new storylines to spice up the ratings . In the fall of 1967, CBS moved My Three Sons to Saturday night at 8: 30 pm . In the season - premiere episode, "Moving Day", the Douglas family and Uncle Charley relocate from the fictional town of Bryant Park in the Midwest to Los Angeles . Robbie (Don Grady) marries his classmate / girlfriend, Katie Miller (Tina Cole). Tina Cole, in fact, had appeared in different roles on three previous episodes of My Three Sons: "House For Sale" from the fourth season (February 13, 1964), "The Coffee House Set" from the fifth season (November 19, 1964), and "Robbie and the Little Stranger" from the sixth season (February 17, 1966). At the end of the 1967 - 1968 season, the ratings had improved from the previous year with the series placing at 24th in the Nielsens . The following season, the newlyweds discover that Katie is pregnant, and she gives birth to triplets named Robert, Steven, and Charles . Although originally played by sets of uncredited twins, these babies were played uncredited by Guy, Gunnar, and Garth Swanson . The most familiar triplets in the show's last two seasons are played by Michael, Daniel, and Joseph Todd . </P> <P> The following year in the tenth season, 1969 - 1970, Steve remarries, taking widowed teacher Barbara Harper (Beverly Garland) as his wife; she brings with her a 5 - year - old daughter, Dorothy "Dodie" (Dawn Lyn), so Steven now had a stepdaughter whom he also subsequently adopts . Also, the last year - and - a-half of the series feature fewer appearances of both Don Grady and Stanley Livingston . Grady's character was written out of the show at the end of the 11th season, which allowed for his wife Katie and their triplet sons to remain within the Douglas household the following season (as a structural engineer Robbie was working on a bridge construction in Peru). Chip and his teen wife Polly (Ronne Troup) (who eloped after Polly's disciplinarian father refused to sanction the marriage) move into their own apartment . </P>

Who played the triplets on my 3 sons