Music composers Richard M. Sherman, left, and his brother Robert B. Sherman, right, are shown on the set of the Disney movie "Mary Poppins" with actors Julie Andrews and Dick Van Dyke. (HANDOUT/REUTERS)

Robert B. Sherman, half of the prolific Disney songwriting duo that composed the music for “Mary Poppins” and authored “It’s a Small World (After All),” which has been described as the most-played, most-translated and most-hair-pullingly-catchy tune on Earth, died March 5 in London. He was 86.

His death, of undisclosed causes, was confirmed by a representative from Walt Disney Co.

Despite a distant and at times hostile personal relationship, Mr. Sherman and his younger brother, Richard, wrote 150 songs that were featured in 27 Disney movies.

They shared two Academy Awards for their work on “Mary Poppins,” the story of a magical babysitter who enlivens a starchy British family — and forever changed the English lexicon by inventing the word “Supercalifragilisticexpialidocious” for that 1964 film.

During their five-decade career, the Sherman brothers drew much of their inspiration from their father, Al Sherman, a Tin Pan Alley songsmith who had an innate sense of the qualities that make a tune stick in listeners’ memories and resonate in their hearts.

Robert and Richard became two of Disney’s chief purveyors of good cheer, having been handpicked by the studio’s namesake for several of the company’s biggest movies of the 1960s.

Their credits from Disney included the bouncy “Let’s Get Together” from “The Parent Trap” (1961); the jazzy “I Wanna Be Like You,” sung by the primate “king of the swingers” in “The Jungle Book” (1967); and the title song, performed by Maurice Chevalier, in “The Aristocats” (1970).

For other studios, the Sherman brothers wrote the music for films including “Chitty Chitty Bang Bang,” the zany 1968 movie adapted from Ian Fleming’s children’s story, and “Charlotte’s Web,” the 1973 animated film based on E.B. White’s book.

Their most enduring success — the film version of P.L. Travers’s novel “Mary Poppins” — began somewhat inauspiciously. Disney called the Shermans into his office and asked a question that, in an era before many American families employed full-time or live-in babysitters, was not unreasonable: “Do you boys know what a nanny is?”

“Yeah,” Richard replied, according to an account in the New Yorker. “It’s a goat.”

In the original movie, the nanny was played by Julie Andrews; Dick Van Dyke was her chimney-sweep sidekick who sang the Cockney-infused “Chim Chim Cher-ee,” for which the Sherman brothers won the Oscar for best song. They also won the award for best overall film score.

Nearly all the numbers on the soundtrack became hits. The title of “A Spoonful of Sugar,” Mary’s song about the virtues of a good attitude and work ethic, was inspired by Mr. Sherman’s young son, who remarked that a lump of sugar made the polio vaccination more palatable.

“Supercalifragilisticexpialidocious” was the result of practiced ingenuity. As boys, the Sherman brothers played a word-invention game at summer camp.

“We wanted something super colossal, and so then, well, supercalifragilistic,” Richard Sherman once told the Sacramento Bee. “Then we wanted an obnoxious word, and atrocious is obnoxious. And, also, you want to sound smart, so you’re precocious, and precocious rhymes with atrocious and that’s, of course, a good rhyme. Then we had three-fourths of the song.”

Robert Bernard Sherman was born Dec. 19, 1925, in New York and grew up in Beverly Hills. He served in the Army in Europe during World War II and was among the first American servicemen to enter the Dachau concentration camp. He also had been shot in his kneecap, a wound that left him unable to walk without a cane.

Especially after his traumatic experience during the war, Mr. Sherman was known as the quieter of the two brothers. They often fought, and in later years were said to have thrown typewriters at each other and sit noticeably far apart during premieres of their own films.

Robert Sherman graduated in 1949 from Bard College in upstate New York. He aspired to write novels; his brother wanted to compose symphonies. Their father attempted to unite them by daring them to write a pop song together. The result was “Gold Can Buy Anything (But Love),” recorded by the singing cowboy Gene Autry in 1951.

Their other successes of the 1950s included “Tall Paul”(which was written with Bob Roberts and performed by Annette Funicello) and “You’re Sixteen” (recorded in 1974 by Ringo Starr).

Perhaps their most famous song — the tune “It’s a Small World” — was written for an attraction at the 1964 World’s Fair. It was a “plea for international peace and friendship,” film music historian Jon Burlingame said in an interview.

Today the song is endlessly piped in over speakers at Disney amusement parks. Mr. Sherman admitted that he and his brother had “driven teenagers crazy in every language.”

In 2008, President George W. Bush honored the brothers with the National Medal of Arts for music that has “helped bring joy to millions.” By that time, Robert Sherman had settled in London.

His wife of 48 years, the former Joyce Sasner, died in 2001. Besides his four children, survivors include his brother, Richard, whose doorbell in Beverly Hills sings “It’s a Small World.”