I'd say no. True stories often have specific details and verifiable sources, and there's no indication that's the case with Larry and Marge. It's probably just a fictional creation.
Aunt Marge could be developed by showing her having a moment of self - reflection. She might realize that her harsh treatment of Harry was wrong and start to be more empathetic. For example, she could see Harry's kindness towards animals and that could change her view of him.
Marge has a few friends in the comic. These friends often help her navigate various situations and add depth to her character. For example, there's Lisa who's always there for her during tough times.
It could develop into a more tolerable one. Harry might start to see Aunt Marge as a pitiful figure rather than just a mean old woman. Maybe he discovers some things about her past that make him more empathetic.