"Joan Lee passed away this morning quietly and surrounded by her family," the spokesperson said in a statement. "The family ask that you please give them time to grieve and respect their privacy during this difficult time."
Joan, a former British hat model, tied the knot with Stan in 1947. They had two children, J.C. (Joan Celia), born in 1950, and Jan, who died three days after her birth in 1953.
Joan was with her husband throughout every era of Marvel Comics, with Stan crediting her for for inspiring much of his success.
"Before you quit, why don’t you write one comic you are proud of?" Stan Stan recalled his wife's words to The Hollywood Reporter last year, remembering a time when he contemplated leaving the business. After that motivation, he said, he created the Fantastic Four.
Decades later, Marvel expanded into film and television, with Joan voicing several characters in '90s animated Marvel shows. She played Miss Forbes in Fantastic Four and Madame Web in Spider-Man. She also made a cameo in 2016's X-Men: Apocalypse.
Joan was also an author herself, writing the 1987 novel, The Pleasure Palace.