Keane created three animated specials for television and published more than 40 books. In 1971, he collaborated with his neighbor, family-humor columnist Erma Bombeck, on "Just Wait Till You Have Children of Your Own!"
In the foreward to another Keane book, Bombeck wrote: "Mostly I admire and respect Bil's gentleness, his warmth, his respect for that battered, floundering, much-maligned institution — the American family."
Among fellow cartoonists, Keane was known to display a hard-edged sense of humor that Lazarus described as "sardonic." Keane softened his approach for the comic strip, aided by a "tremendous memory" that made it easy to come up with ideas, he later said, and perhaps to continue to see the world through the eyes of a child.
In one panel of "The Family Circus," Jeffy holds a snapshot of his father as a boy and asks, "Mommy, when did Daddy get little?"
Keane is survived by his five children, Gayle, Neal, Glen, Christopher and Jeff; nine grandchildren and one great-grandchild.