Thomas Rockwell, who grew up as a character in the illustrations that his father, Norman Rockwell, created for The Saturday Evening Post and later became a successful author of children’s books, including “How to Eat Fried Worms,” a gross-out novel devoured by millions of grade-school students, died on Sept. 27 in Danbury, Conn. He was 91.

The cause of his death, in a hospice facility, was Parkinson’s disease and other ailments, his daughter, Abigail Rockwell, said. He had lived for many years in a converted chicken shed near Poughkeepsie, N.Y., a setting that evoked the small-town backdrop of his father’s artwork.

Mr. Rockwell appears in several of his father’s well-known works: as a mischievous boy sitting at his sister’s dressing table and reading her diary; flexing his not-very-big muscles in a mirror, a dog at his side; and as a high school graduate, in cap and gown, clutching a rolled-up diploma.

Posing for a painting that depicted him rummaging through his grandfather’s overcoat pocket was one of his favorite childhood memories, he told Cobblestone, a children’s magazine, in 1989. That image appeared on the cover of The Saturday Evening Post in 1936.

“I had to stand on tiptoe while reaching into the overcoat, which was hung on an easel,” Mr. Rockwell said, describing how his father had composed the painting. “My father gave me a present for posing, and I remember feeling so proud and pleased that I’d helped him with his work. I know I’ve never enjoyed any gift as much as that one.”

Norman Rockwell, who died in 1978, wanted his children to become artists, even though he sometimes said otherwise.