There have been American theater families for as long as there has been American theater. The Booths and Barrymores are the standardbearers. Current clans includes the Fosters (actor siblings Hunter and Sutton), the Marshalls (director-choreographers Rob and Kathleen), and the Naughtons (dad James and children Greg and Keira all are thesps). A tribe on the brink of greater visibility may be the Gerstens.

The silver-haired, avuncular Bernard Gersten, a man whose career parallels the history of nonprofit theater in New York City, forms the trunk of this family tree. He was associate producer of the New York Shakespeare Festival from 1960 to 1978, and has been executive producer of Lincoln Center The ater since 1985. The two companies are arguably the most important nonprofits in the city.

Daughter Jenny is the associate producer of the Williamstown Theatre Festival, which kicks into high gear this week. In the position since 1996, she is a leading candidate to become the lauded summer theater’s next producer. (She is also married to “A Year With Frog and Toad” lyricist Willie Reale, and sister-in-law to Willie’s composer brother Robert.)

Finally, Bernie’s playwright-actress niece, who shoulders the loaded moniker of Alexandra Gersten-Vassilaros, recently came into her own with “Omnium Gatherum,” a 9/11-born collaboration with Theresa Rebeck that played Off-Broadway last season and was nominated for a Pulitzer prize. Her latest play, “The Argument,” will get a reading at New York Stage and Film’s Vassar College digs on July 24.

“Going into the theatre was a rather automatic choice,” said Alexandra, whose father Leon, Bernie’s younger brother, was a stage manager and later worked on Sid Ceasar’s “Your Show of Shows.” “It was so inbred, so much a part of our enthusiastic selves.”

“My father must have known we were going to be in the theatre,” echoed Jenny, whose mother is Cora Cahan, one-time executive director of the Feld Ballet and now president of the New 42nd Street, the nonprofit organization that oversees the preservation and operation of the historic theaters on 42nd Street.

“He was always saying ‘There are all those “ologies” out there. There’s archeology to zoology. I don’t want you to think that because both your parents work in nonprofit arts that that’s the only choice you have.’ ” Jenny dutifully followed dad’s advice and majored in archeology at Oberlin College (Ms. Gersten-Vassilaros attended NYU). Upon graduating, however, she made a beeline for the theater. “I never made it to zoology.”

The elder Gersten has a theory about why some progeny of theatre people follow their elders’ example. “When children of performing arts parents sense a certain well-being on the part of the parents, then the field seems attractive to them,” he said.”My wife and I were content.”

When Bernie was associate producer of the New York Shakespeare Festival, the festival’s flamboyant impresario, Joseph Papp, was often over for dinner, blowing cigar smoke and singing Irish ballads. (“We only had one or two,” said Bernie. “But we sang them repeatedly.”) Also at table were the likes of Raul Julia, Sam Waterston, and John Guare. When Jenny was two, Bernie handed her across the St. James Theatre footlights to Julia after a performance of NYSF’s “Two Gentleman of Verona”: her first bow.

For some years, Bernie’s family and Alexandra lived in the same Manhattan building. Alexandra, who is nine years Jenny’s senior, used to babysit her cousins Jenny and Jilian, now a program creator for the after-school corporation, a nonprofit. “She was the older cousin who would teach you about sex and tell you about her bad dates,” Jenny said.

Alexandra, a golden-haired extrovert whose natural enthusiasm heats a steady boil of bubbly conversation, remembers seeing Eric Bogosian’s “Talk Radio” with a teenage Jenny. “And I could see she had a lot of ideas about the play. Since I knew she was interested in theater, there was some consciousness on my part to draw her out. We actually had our first conversation about what a play is. That was a moment where I could see becoming a peer of hers.”

The tie has persisted.Alexandra both acted and wrote for the 52nd Street Project, where, beginning in 1991, Jenny moved up from intern to director of marketing and development. Alexandra has also been employed as actress and playwright at Williamstown.

This year’s Williamstown season – current producer Michael Ritchie’s last – opened (somewhat ironically) with “Water’s Edge,” a new play by Alexandra’s writing partner, Theresa Rebeck. Kate Burton starred, as she will in a lavish mounting of “A Midsummer Night’s Dream,” beginning July 14.

Bernie dutifully sees almost everything Williamstown produces. “The achievement of the last number of years has been exceptional,” he crowed. Does he ever offer his advice? “Carefully,” he allowed.

Concerning Jenny’s chances at Williamstown, Bernie said, “I think what she has is judgment. Producers exercise an opinion.They are judged by what they do. Jenny shows both the judgment and the desire to pick out that one play.”

Should she become producer, Jenny would in a few years seem to possess all of the qualifications needed to succeed her father at Lincoln Center (though the elder Gersten – who,like his niece, studiously deflects inquiries regarding age – shows no sign of retiring). “I made a joke during the recent production of ‘King Lear,’ ” said Jenny, “That the play was really about me, and I wanted to take over the theater.”

Don’t look to Bernie for dire pronouncements on the future theatre world his daughter will inherit; his optimism borders on the Pollyannaish. “I don’t despair of the theatre, as some people do,” he said. “I allow that the end of the theatre may happen sometime in the future. But doomsday is not imminent. I have worked continuously in the theatre for an extraordinarily long time. I know how unusual that is. It’s hard to earn a living. But I have a core belief that people don’t work in the theatre and hate it.”

All the family gathers each year for Bernie’s annual seders (which the irreligious Gersten described as “cultural” and “celebratory”), filling out a table that stretches through two rooms.”This year’s seder was on the same day that “Omnium” was short-listed for the Pulitzer Prize,” recalled Alexandra. “Bernie had something to say about that.Then we read the Haggadah.”

Alexandra, by the way, bravely ventured outside the theatre to find her spouse. He is John Vassilaros, thirdgeneration owner of Vassilaros coffee, whose company supplies the city’s diners and food carts with a steady flow of java. (The two are actually fourth cousins, whose ancestors hail from the same Aegean island town.) He is known in the family as “Johnny Coffeeshopolis.”

Meanwhile, the third generation is being subtly groomed. Alexandra had her eldest boys sit backstage when she performed Off-Broadway last winter in Nicky Silver’s “Beautiful Child.” “Just like I sat when my father was the stage manager at Mineola Playhouse,” she recalled. And Jenny’s son Gus was offered the role of the changeling boy in Williamstown’s upcoming production of “A Midsummer Night’s Dream.” He turned it down, however, with the reply “Mom, I just want to play baseball all summer.”

Bernie raised an eyebrow when he learned of his grandson’s refusal – until he heard what the role was. “Oh, the changeling boy,” he scoffed. “That’s just a carry-on. No lines!”