That’s not precisely true,
according to Peter David in an article originally published in 1998. It was Stan Lee’s idea, and Stan was writing the newspaper comic strip, which technically makes the marriage a writer-driven idea.
“Stan became enamored of the notion of Peter getting married both in the comic and in the comic strip, and more or less steamrolled it through by going public with it before any of the powers-that-be could talk him out of it. Me, I thought it was a nifty idea, but no one ever accused me of being excessively smart.”