THE HAGUE, Netherlands — Dick Bruna, the Dutch “spiritual father” of Miffy, the white rabbit who enchanted millions of young children around the world for more than half a century, has died at age 89, his publisher announced Friday.

Decades before Instagram made square images immensely popular, illustrator and artist Bruna understood their power. For years, his Miffy books were printed in a square format.

“He thought that size was really good for two little children’s hands, and he loved the visual impact, too,” longtime friend Marja Kerkhof, of his Dutch publisher Mercis, said in a telephone interview.

Bruna “passed away peacefully in his sleep” Thursday night in the central Dutch city of Utrecht, Kerkhof said.

The simplicity of Bruna’s characters drew adoration not only from children, but also from adult art lovers. Amsterdam’s venerable Rijksmuseum put on a show featuring his work in 2015.

He wrote and illustrated a total of 124 books, but Miffy, known in the Netherlands as Nijntje, a contraction of the Dutch word for rabbit, was far and away his most popular and best known character.

Bruna created 32 books about the rabbit, which were translated into more than 50 languages and sold more than 85 million copies, Kerkhof said. The man his publisher described as Miffy’s “spiritual father” stopped drawing in 2011.

Miffy, who turns 62 this year, is a merchandising juggernaut, featuring on stationery, toys and children’s trinkets sold across the world as part of a multimillion-euro (dollar) business.

“He was very much loved around the world. I remember traveling with him to Australia, to New Zealand, to Asia, to Japan. Wherever he would go, people would queue up for signing sessions of his books,” Kerkhof said.

She said the public’s affection for both Bruna and Miffy stemmed from the illustrations’ simplicity.