One of the most famous children's books in America is Maurice Sendak's WHERE THE WILD THINGS ARE. The story, in short, is about a very bad little boy named Max who is sent to bed without dinner one night because he's been so naughty. But as soon as he gets to his room, The Wild Things-- wonderful monsters of all shapes and sizes-- appear and they all play happily together till morning. Max is delighted and has no fear of them. He's a brave little guy. Sendak has said readers often ask what he thinks happened to Max when he grew up. One night years ago the author was at a dinner party in New York. Seated next to him was the actress Sigourney Weaver. It turned out the glamorous Weaver was a big fan of his work and they chatted throughout the meal. Later she pointed to a man sitting across the table. She said he was her husband and one of the reasons why she fell in love with him was he reminded her so much of Max in WHERE THE WILD THINGS ARE. Delighted, Sendak said he finally knew what happened to his famous character: Max grew up and married Sigourney Weaver.
And that’s what he tells anyone now when they ask what happened to the boy.
I've found a number of quotes online which mention that the monsters in Where the Wild Things Are are based on the way Sendak's more annoying relatives looked to him when he was a kid, but none which included a detail that I heard in an NPR interview with him-- that he tried to invent entirely new monsters, and then realized they were based on his relatives.