I think if you are going to expand upon the story, the first chapter should be for establishing the characters and whi they are as individuals. I would recommend drawing out the relationship between these two, and deffinetly put some conflicts in the relationship that come about from something like opposite personalities and didferent interests or views. How the characters react is up to you, but I think this is a great basis for a story.
Like they are in they present, and sometimes both of them think about their past which actually will tell both their perspectives in the story