The last appearance of Robbie Douglas that I remember was just before he went to South America on business. He and Katy were laying in bed and he told her that he was very happy. Did he ever get back to Katy and their kids?

If he did, it was never shown on the series. He was absent for the final year of the show, and he didn't return for the last episode.

Its A Coincidence On M3S Don Grady has left M3S And Robbie Is sent To South America but never returns

On Dallas Jim Davis Has died and Jock is sent To South America Only to have him killed in a Helicopter Crash.

I Wonder somewhere If Robbie has ever met Jock Ewing down there.

Hmmm...

You know, Ronne Troup (Polly) appeared on "Knots Landing" for a while as a babysitter. Some strange MTS/Ewing connection going here? And didn't Jock Ewing have three sons (at least when the show began)?

Yes Jock Ewing Had Three Sons J.R. (Larry Hagman),Gary(David Ackroyd(1979) and Ted Shackelford(1979-1993) and Bobby (Patrick Duffy) In The 1980-1981 Season It was Revaled that Ray Krebbs (Steve Kanaly) Was The Fourth Ewing Son. Also Ben Cartwright (Lorne Greene Had Three Sons (Each By Different Marriages) Adam(Pernell Roberts),Hoss(Dan Blocker) And Little Joe(Michael Landon) Jamie Hunter (Mitch Vogel) Was Later Adopted by The Cartwrights
Victoria Barkley Had Three sons in Jarrod(Richard Long,Nick(Peter Breck),Eugene(Charles Briles) and Heath turned out to be the fourth son by Victorias Late Husband Tom Barkley. The Bradys Have Three boys in Greg(Barry Williams),Peter(Chris Knight) and Bobby (Mike Lookinlad) and The Partridges Have Three Keith(David Cassidy),Danny(Danny Bonaduce), and Chris (Jeremy Gelbwaks(1970-1971) and Brian Forster(1971-1974)

Some shows Do have a "My Three Sons" Of Their Own.

I remember Robbie and Katie moved to San Francisco in one episode and made new friends etc due to his being laid off? Then, he is in South America??? How did they explain all of this????

The last episode of the 11th season was the pilot for a proposed spinoff with Robbie and Katie living with the twins in SF. The spinoff was not picked up, and Don Grady chose not to return to M3S. So in the first episode of the 12th season, it was explained that Robbie had been temporarily transferred to South America, and Katie moved back in with his family while he was away, so they could help her out with the triplets.

Katie moving back in with Robbie's family doesn't sound like very good logistics. In the Douglas house, Steve and Barbara had a room, Ernie had a room, Dodie had a room, and Uncle Charley had a room downstairs. That is all the bedrooms that we ever see in the house. So where did Katie and *3* boys, who were 3 years old by that time, stay?

On the other hand, Katie had her grandmother and her aunt who lived at that house in Glendale (which we see around the time of R * K's wedding). And if they no longer lived there, for whatever reason, Katie's mother presumably lived alone in St. Louis. It should have made more sense for Katie to take up residence with her family rather in than the crowded Douglas home.

The obvious answer is that this was television, and they were the characters we still wanted to see together-- or as many of them as were still available and willing.

NOw with Robbie gone, How could it still be called My 3 Sons?

Thats a good question When Don Grady Left M3S They didn't find maybe a younger boy to fill the "Three Sons" Gap Since that was already done when The Show moved from ABC To CBS In 1965 And Tim Considine Left only to be replaced By Barry Livingston. They probably left it so that If Don Grady Came back there would be still M3S In fact you could the Triplets as M3S Since they were on there already.

This is probably further support that the show stayed around beyond its time. I say this reluctantly, because I remember being a fan of the show as a kid, and we don't like to just scrap a TV family we feel so much at home with. But M3S simply could not be what it was created to be, beyond a certain point. Kids do grow up, families do change, and time is real and unbendable (with apologies to Einstein).

To many of us, it would have been a blast for the show to continue and to watch the triplets grow up and go to school, play sports, have girlfriends pick out the wrong boyfriend (who looked identical) on a visit. But it just wasn't to be.

I think they just wanted to keep it on, into the early '70's, so we could see how the whole family managed with being married, having triplets, and adopting a little girl(Dodie)