What flashback does Brandon have, and what does it reveal about his father?

I'm not sure what "flashback" or section of the book you are referring to, but while Brandon and Lowery are attempting to escape, Brandon has a flashback to a moment in which his father tells him that they are a team.... that together, they will survive. This flashback speaks to Brandon's father's great love for him... their bond, and their loyalty to one another.