I could not find the story that is missing in your question but I will tell you something more about Cortazar that might help you.
Julio Cortazar wrote short stories, essays, and novels. He is also known as one of the founders of the Latin American Boom which is a literary movement originated in the 60s and 70s. It flourished when a group of young Latin American novelists started to circulate in Europe.
That is why he might reflect as a South American writer. He also influenced all the people of Spanish-speaking generations and writers in America.
“Beside” is the preposition and “him” would be the object of the preposition. Ask yourself this question when finding the object of the preposition. Where is Jill working? Beside HIM.
