Stan's spokesperson confirmed the news to The Hollywood Reporter.
"I can confirm the sad news that Joan Lee passed away this morning (Thursday) quietly and surrounded by her family. The family ask that you please give them time to grieve and respect their privacy during this difficult time," the spokesperson said.
Before meeting Stan, Joan married an American soldier during World War II, where she was extremely unhappy.
After a six-week stay in Reno, Nevada, a judge granted her divorce and the former British hat model had then tied the knot with the veteran comic-book writer on December 5, 1947.
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She did voice work on the "Fantastic Four" TV show portraying the character Miss Forbes and even had a small appearance in "X-Men: Apocalypse".
Joan also wrote a 1987 novel, "The Pleasure Palace", about a man striving to build the most luxurious ocean liner ever while romancing several women at once.
Stan, 94, has a daughter Joan Celia Lee with Joan. Their
Another child, daughter Jan Lee, died three days after delivery in 1953.