Adult siblings represent one of those interesting relationships that have received relatively short shrift in primetime given the fertile dynamics, a situation Fox seeks to rectify with the sweet-natured new sitcom “Ben and Kate.” Starring Dakota Johnson as (yet another) single mom, and Nat Faxon as her childlike older brother who, with his penchant for “hare-brained” schemes, functions as the Lucy to her Ethel, it’s a comfortable thematic companion to a lineup anchored by “New Girl.”

Ben parachutes back into younger sis Kate’s life, even as she’s braving taking a plunge into a relationship, having been mostly sidelined by her 5-year-old daughter (Maggie Elizabeth Jones). In this endeavor she receives not-always-helpful coaching from her fellow bar worker BJ (Lucy Punch), to whom Kate insists, unconvincingly, that she is “amazing at getting laid.”

Ben, meanwhile, has come to town because an ex-girlfriend is getting married, harboring a sort-of “The Graduate”-like dream of sweeping her away at the last moment. (It’s an amusing and somewhat unfortunate coincidence that both “The Mindy Project,” which premieres the same night, and this show feature weddings as backdrops to help establish the characters, seemingly recognizing they bring out the best and worst in people.)

Created by Dana Fox and directed by Jake Kasdan — reunited after working on “New Girl” — the show’s central conceit is that Ben and Kate bonded during a difficult childhood, and still try to look out for each other. In economical flashbacks, they’re shown as kids taking refuge under the kitchen table when their parents fought, which lends emotional resonance to the proceedings.

Whatever their personal shortcomings, there’s a warmth in their interaction, manifesting itself in protectiveness and advice, which each of course gives better than follows.

Halting and vulnerable, Johnson is pretty adorkable in her own right (although that term should perhaps be retired), and Faxon — who has the more demanding task, coming across as immature but not irritating — delivers a couple of funny moments, including his pained struggle not to curse in front of his young niece.

The danger here, as with any series built around such a low-octane concept, is finding enough story to sustain the show on a weekly basis. Because however appealing the central duo are, their thinly drawn friends are less so, and if the series becomes the bad relationship of the week, “Ben and Kate” could easily grow tedious.

For now, though, there’s a fair amount here to like — at least enough to warrant another family gathering in front of the TV, if not under the table.

Ben and Kate

Fox, Tues. Sept. 25, 8:30 p.m.

  • Production: Filmed in Los Angeles by Chernin Entertainment in association with Twentieth Century Fox Television. Executive producers, Dana Fox, Peter Chernin, Katherine Pope, Jake Kasdan, Neil Goldman, Garrett Donovan; producer, Randy Cordray; director, Kasdan; writer, Fox.
  • Crew: Camera, Uta Briesewitz; production designer, Richard Toyon; editors, Steven Welch, Hugh Ross; music, Michael Andrews; casting, Anya Colloff, Michael Nicolo, Jessica Munks, Brett Greenstein, Collin Daniel, Sherie Jane Hernandez. 30 MIN.
  • Cast: Kate - Dakota Johnson<br> Ben - Nat Faxon<br> Maddie - Maggie Elizabeth Jones<br> BJ - Lucy Punch<br> Tommy - Echo Kellum