William Schallert and Patty Duke in 1964. (ABC Photo Archives/ABC Photo Archives/Disney via Getty Images)

William Schallert, an actor who played Patty Duke’s father — and uncle — in her 1960s sitcom and led a long, contentious strike for actors, died May 8 at his home in Pacific Palisades, Calif. He was 93.

His son, Edwin Schallert, confirmed the death but did not disclose the cause.

Mr. Schallert was usually seen in supporting roles, but his lean, friendly face was familiar to baby boomers for roles in two classic sitcoms — as a teacher to Dwayne Hickman and his pals in “The Many Loves of Dobie Gillis” and as the dad in “The Patty Duke Show.”

“The Patty Duke Show” (1963-1966) was challenging for Duke, who had already achieved stardom on Broadway as the young Helen Keller in “The Miracle Worker” and repeated the role in the film, winning her an Oscar for supporting actress. (Duke died in March at age 69.)

In the television series, she played a double role, as Patty Lane, a typical American teenager, and her cultured cousin Cathy, who lives with Patty’s family. Cathy was newly arrived from overseas, where, the theme song told viewers, she “adores a minuet, the Ballets Russes and crepes suzette.” Patty, meanwhile, just likes rock-and-roll and hot dogs.

Mr. Schallert was cast as Patty’s harried father (and Cathy’s uncle), who was confused by the look-alike girls.

He was similarly frustrated as Mr. Pomfritt, the English teacher on “Dobie Gillis.” The show, which ran from 1959 to 1963, starred Hickman as a teenager comically yearning for the perfect girl and featured a strong supporting cast including Bob Denver as his beatnik pal Maynard. “You ready, my young barbarians?” Mr. Pomfritt would ask his students, comically pining for the days of corporal punishment in the classroom.

In 1979, Mr. Schallert was elected president of the 46,000-member Screen Actors Guild. The next year, he led the union as it staged a 13-week strike over such issues as actors’ pay for films made for the then-new cable television industry.

He told the Los Angeles Times his message to actors was that “we have to respect ourselves as artists” and recalled the pre-union days when actors were sometimes expected to work until midnight and be back at work six hours later.

Mr. Schallert was defeated in his bid for a second two-year term as SAG president in 1981 by “Lou Grant” star Ed Asner, who had strongly criticized the agreement the union had reached to end the strike. Asner ran into his own controversies as SAG chief by taking stands critical of U.S. foreign policy, and he decided not to seek a third term in 1985. He was succeeded by none other than Mr. Schallert’s former screen daughter, Duke.

Mr. Schallert said in 2008 that his greatest accomplishment as SAG president was the formation of a committee for performers with disabilities. “We had established committees for all of the various ethnic minorities, women and seniors,” he said. “I’m a big beneficiary of that right now because I’m 85 and I still work.”

William Joseph Schallert was born in Los Angeles on July 6, 1922. His father, Edwin Francis Schallert, was Los Angeles Times drama editor from 1919 to 1958.

Mr. Schallert attended the University of California at Los Angeles and went to England on a Fulbright scholarship in 1952. He studied repertory theater and lectured on American theater at the University of Oxford.

His wife, actress Leah Waggner, died in 2015. Besides his son Edwin, survivors include three other sons and seven grandchildren, the New York Times reported.

At the start of his career, Mr. Schallert was a founding member of the Circle Theater in Hollywood. The director was Charlie Chaplin, whose son Sydney was a cast member.

In all, Mr. Schallert appeared in hundreds of movies, television series and specials, playing characters and walk-ons. Among his later TV roles were guest shots on “Desperate Housewives” and “True Blood.” In 2008, he played Supreme Court Justice John Paul Stevens in “Recount,” HBO’s Emmy-winning dramatization of the 2000 presidential election.

He also played such real-life figures such as Gen. Mark Clark in the 1979 miniseries “Ike: The War Years” and Gen. Robert E. Lee in the 1986 miniseries “North and South, Book II.”

In an interview with the Los Angeles Times in 1966, Mr. Schallert lamented being cast as “the second man through the door,” or supporting player.

“I did come close to a lead once,” he said. “This was a pilot I made for a series named ‘Filbert.’ But when the producers calculated the series would cost $75,000 per episode, they figured a top name would be needed in the lead to assure success. So they gave up the project. It was a hard pill to swallow.”

— Associated Press