The line here means that a bad or good time passes by, but people who have endured that time remain. In case of Jacopo and Nicola too, they did come for good cultured backgrounds, they were refined and well brought up children. Even though, they were going through a tough time now after the war, they still remained cultured and well mannered. They were extremely hard working, and did not allow the war to have a negative impact on their lives. The boys did all kinds of odd jobs to pay for their sister’s treatment, but never allowed the conditions of their work to change their personalities. They were young, energetic, enthusiastic , cultured young men before and even after the war.