I generally agree with the other poster's comments here, but as one who grew up in the relative same era in which the series' story lines existed, who saw the series in first-run syndication, may view it from a slightly different perspective.
"tvpdean's" comment that Brian Keith's character on "Family Affair" was always "railing against fate," implying he was somehow brash or hard-nosed with his juvenile charges, strikes me as way off base. In fact, what was so appealing & endearing about Keith's portrayal of engineer/playboy "Uncle Bill (Davis)" was that he WAS a "tough guy" who was very gentle and reasonable with his two nieces and nephew, albeit with the help of his manservants, "Giles French" (and, briefly, "Niles French"). Not that Keith's character was above sometimes shouting in frustration, but that's only human in any situation. Keith's "Bill Davis" was a helluva lot more realistic than Forsythe's "Bentley Gregg" on this series, though actually Forsythe would play the sort of character "tvpdean" implies Forsythe was on this series in another, later sitcom, "To Rome With Love," which was produced by Don Fedderson, the same guy who created "Family Affair" and "My Three Sons" (and who also produced Betty White's first series, "Life With Elizabeth").
Also, it was certainly not "apparent" this series' family lived in an Eastern or Midwestern city. What with "Gregg" running around with all sorts of starlets and their driving in an open convertible all the time (as "Mike Tee Vee" so duly noted), I'd say it was rather suspiciously like sunny, Southern California. It would also make sense that it would be West Coast, where in those days there was much more an influx of Asian persons, such as houseboy "Peter Tong," than on the East coast or in the Midwest.
"tvpdean's" assertion this series was an ancestor of single father figure dating shows is right on the mark, however, and "The Courtship Of Eddie's Father" is a good analogy, although Bill Bixby's character on that show was an actual father, not an uncle (as Forsythe is here); and also, Bixby's character was a widower, whereas Forsythe's "Gregg" was, presumably, never married. But "Bentley Gregg" and Bixby's "Tom Corbett" (not to be confused with "Tom Corbett, Space Cadet") did have one, other trait in common--Asian servants; the aforementioned "Peter" on "Bachelor Father" & "Mrs. Livingston" as housekeeper to "Mr. Eddie's Father" (and babysitter/governess to master "Eddie" himself).
So actually, "Bachelor Father" has much more in common with "Family Affair"--a single uncle, with a manservant of foreign ethnicity, who adopted his niece and is leading an active romantic life. Although, in the later years of "Family Affair," Keith's "Uncle Bill" became much more domestic, less the globe-trotting playboy (except when his jobs took him out of NYC).
By the way--Noreen Corcoran, who played "Kelly" on this series, was part of a large family of kid actors that included Disney ensemble regular Kevin Corcoran ("Moochie" on the "Spin & Marty" episodes of "The Mickey Mouse Club," Tommy Kirk's younger brother in "Old Yeller" & "The Shaggy Dog," and himself star of Disney's circus boy film, "Toby Tyler." And since I brought him up, Sebastian Cabot was not, as commonly believed, British. Rather he was a Canadian citizen--which, I realize, would still make Cabot a British subject, but would hardly explain his British-sounding accent. I think that was "cultivated" for effect, much as William F. Buckley's upper crusty inflection.
