The film has been a part of millions of childhoods for decades.
But what many fans don’t know is that Matthew Garber’s acting career ended abruptly – and tragically.
Starring in Mary Poppins at just eight years old, Matthew also starred in two other Disney films, The Three Lives of Thomasina and The Gnome-Mobile.
As he entered his teenage years, Matthew stepped away from acting for several years.
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But little did he know, he would never appear on film again.
On a holiday in 1976, Matthew unknowingly contacted hepatitis.
He was unaware that he had the disease, and by the time he returned home to London, the disease had spread to his pancreas, becoming untreatable.
Just a year later, the actor passed away at 21 years old.
At the time, speculation arose that Matthew had contracted the disease through drug use, however his brother Fergus denied the claims, adding that the hepatitis likely came from consuming “bad meat”.
Following Matthew’s death, Karen spoke about the loss of her on-screen brother.
"I can't imagine making movies would have been half as much fun without him," she said.
"He loved being naughty, finding and jumping off of small buildings on the back lot," she added.
"He did live a full life over his 21 years."
Karen's acting career dwindled away not long after she starred in Mary Poppins.
After a brief run as Desdemona in the 1981 Broadway production of Othello, Karen retired from show business all together.