Keane died Tuesday of congestive heart failure at his longtime home in Paradise Valley, Ariz., according to King Features Syndicate, which distributes the daily comic.
"The Family Circus" appears in nearly 1,500 papers around the world today, making it the most widely read syndicated panel, according to King Features.
"He was so marvelous. I always felt that he had a great sense of truth," said Mell Lazarus, creator of the "Momma" comic strip. "He had a vivid imagination. It's one of those cannot-miss features."
The strip's characters remained largely the same age year in and year out — an ageless suburban mother and father and their four children, Billy, 7; Dolly, 5; Jeffy, 3; and PJ, 18 months. The daily panels were routinely drawn within a circle, which underscored their sense of closeness, according to the syndicate.
Like many humorists, Keane mined his own family for material. He admitted to modeling the bespectacled and often befuddled Daddy on himself. His wife, Thelma, was the inspiration for the always-loving and ever-patient mother, also named Thel.
"When the cartoon first appeared, she looked so much like Mommy," Keane told the Associated Press after his wife died in 2008, "that if she was in the supermarket pushing her cart, people would come up to her and say, 'Aren't you the Mommy in "Family Circus?"'"
The children in the strip were largely composites of his own five, but PJ "is the best of all my children: cute, usually smiling, once in a while naughty," Keane told the San Jose Mercury News in 2004.
In one cartoon, Jeffy tells a friend: "His name is PJ — but most of the time, he's called No-No."
"I don't just try to be funny," Keane told The Times in 1990. "Many of my cartoons are not a belly laugh. I go for nostalgia, the lump in the throat, the tear in the eye, the tug in the heart."
"The Family Circus" plugged in to the universality of the family experience, and readers related, said Andrew Farago, curator of the Cartoon Art Museum of San Francisco.
"Kitchens coast to coast have 'Family Circus' strips cut out of the newspaper on them," Farago said, "because you will be reminded of something that your sister did or what your father said at breakfast."
William Aloysius Keane was born Oct. 5, 1922, in Philadelphia to Aloysius William and Florence Keane and grew up in suburban Crescentville, Pa.
Self-taught as an artist, he started out imitating the style of New Yorker cartoonists in the late 1930s. After Keane drew cartoons for four publications at his parochial high school, he realized that he had found his life's calling, he later said.
His parents could not afford to send him to art school, so after high school he worked as a messenger at the Philadelphia Bulletin newspaper — and observed the staff artists.
While putting out a satire magazine, the Saturday Evening Toast, with a group of friends in the late 1930s, he changed the spelling of his first name to "Bil" because the other artists on the project were altering their names.
He spent three years in the Army during World War II, drawing for Yank magazine and the Stars and Stripes newspaper. Keane also sold cartoons to a national magazine and met his future wife while stationed in Brisbane, Australia, where they shared office space. He married the native Australian in 1948.
From 1945 to 1958, he was a staff artist for the Philadelphia Bulletin and continued to free-lance as a cartoonist.